World of Darkness isn't D&D, and citations may not always be feasible.
I want to make clear at the outset that I do agree with you, and where proper citations and rule references are possible they should be included. I try to do this where possible when answering WoD questions, but it isn't always possible or especially desirable.
There are a few features peculiar to WoD that I think affect how reasonable a citation is:
1. WoD is huge and distinctly organized
There are a lot of products released under the World of Darkness label, and they're pretty scattered in what they cover. The "basic" rules are not strongly comparable across all of these. They're all d10 games, but as each subfranchise under WoD tries to evoke WoD's themes for totally different types of supernatural creatures mechanics often aren't very portable.
As an example, the way that werewolves are detailed in Vampire: the Masquerade books is very different from how they are detailed in Werewolf: the Apocalypse books, to the extent that they're not exactly describing the same thing. In V:tM, werewolves are described by vague applications of abilities unique to V:tM rather than the "proper" rules that are used in W:tA. The mechanics that govern vampires are totally different from those that govern werewolves, so these awkward translations are really the best that can be done.
The upshot of this is that there is often little ambiguity in which books are meant for most questions. If you have a question about V:tM, the answer is almost certainly in the V:tM core rulebook. Some more precise questions (say, about a specific clan in V:tM) will draw from the splatbook for that clan, and there are rarely alternatives to choose from. In cases where there legitimately are multiple possibilities it seems to me that people generally do offer citations (examples include updated books disagreeing with previous versions within an edition, or rules which may plausibly be spread across multiple books).
There is some confusion that arises from poorly named editions of the games (old WoD vs. new WoD, Theater of the Mind vs. 2nd Edition vs. Revised vs. V20 vs. Chronicles vs. V5), but typically tags on the question are specific enough to head it off.
A big part of the WoD games is the metaplot-- the "true" story of what's going on behind the scenes. Many questions that aren't about specific mechanics touch on this in some way, and the answers (to the extent that any exist) are spread across every conceivable product in ways subtle and explicit. The metaplot is, famously, not consistently described, meaning that generally citations are not definitive in answering the question. This was, allegedly, by design, to foster creativity in specific Storytellers.
In practice, it's simply unclear what is canonically true and what isn't. As RPG.SE isn't a forum it's not a good place to discuss which citations should prevail over others, or what abandoned plot points are still in force (I'm looking at you, Secrets of the Black Hand Vicissitude parasites!). Some of the sourcebooks that provide (commonly accepted to be) canonical answers don't even have rules in them-- there are WoD novellas and comics.
The result of this is that it's extremely difficult to discern the truth of an answer from trolling the books, and the effort of doing so is immense. Providing citations is great for indicating the thought behind a position, but aren't definitive in the way that they generally are for D&D. It's a bit like trying to describe the specific properties of Miska, across all editions of D&D at once, for a huge proportion of questions.
3. As an aside...
A lot of canonically true information does exist in the books, but in a particularly casual style. Most of the books include multiple, long narrative sections full of detail and with annotation-style comments (also providing game-relevant information) tacked on. In many cases this would be hard to cite-- it's an observation by an in-universe character reading or recounting the narrative section and commenting on it. The annotation doesn't include enough context to be a citation on its own, and citing the context can often result in a massive block of quoted text from which it is hard to extract the salient information.
4. WoD is a mess
I mean no disrespect. V:tM was the first tabletop game I ever played or ran, and I think highly of World of Darkness in many ways. But it's simply full of inconsistencies and other problems which make scope awkward in approaching questions. I mentioned above the difference in how werewolves are represented in their own product vs. in other books under the WoD franchise. If a querent comes here asking a question about werewolves, it's not totally clear which would be the authoritative answer.
If the querent only has the V:tM core rulebook, would they be able to use an answer drawing from W:tA? Or might their problem be that the awkwardly-translated werewolf information in V:tM is too shallow and one-dimensional to use in the way they want? Should answerers expect the querent to buy and use the W:tA core rulebook? The WoD products aren't unified in the way that D&D books are, and without requiring askers to list all specific products whose contents might be valid it becomes hard for answerers to even identify the correct set of rules from which to offer an answer.
The White Wolf wiki is particularly bad about this.
5. WoD questions are often broad and poorly specified with respect to cite-able information
One of your example questions (the one about learning magical Disciplines) had an answer from me which contained no citations. The reason I didn't cite anything there was because answering the question in a comprehensive way with citations would require dozens of citations. There are more than a few magical Disciplines in V:tM, and they have varying amounts of things in common with each other (it's not at all like comparing an arcane spellcaster to a divine spellcaster, for example).
I won't say that it was necessarily appropriate to not add citations, but to hunt down and add each one for each style of magic that had an answer would take ages. My answer (though not popular) is correct, even though it doesn't cite the nameless annotator in Blood Magic: Secrets of Thaumaturgy expressing (multiple times) that unapproved individuals learning Thaumaturgy are to be executed by the Tremere clan across a narrative section written by another unnamed character.
6. SE factors
We all know about the odd incentives that the SE format can introduce. It's a simple truth that WoD questions are fairly niche and rare here, meaning that there are relatively few users ready to assess how reasonable a citation is. And there is a particularly short timeframe to post an answer and collect whatever few upvotes are ever going to be available for a given WoD question, turbocharging the drive to get an answer in right away.
And since adding WoD citations is difficult, time consuming, not definitive, and often (apparently) of little value to querents, it doesn't surprise me that answerers often determine that fully-cited answers aren't necessary for some questions.
I really do think that there are reasons that providing citations is more difficult and less useful for WoD questions than for many, perhaps most, other game systems.
There are still many questions for which citations are definitely appropriate and helpful, and those should include citations. For others, demanding citations in all answers will only make answers worse (or prevent answers from being posted in the first place). I don't know how to gauge where the line between those question types is, or how to respond to an answer lacking citations when they should be present (short of posting my own answer).