Why do characters with a high prime requisite gain bonus XP?
The question presents some information, then asks:
What is the reason for this rule? Did the game's designers ever explain it, either officially or anecdotally?
Is this a "designer reasons" question that should be closed, since "designer reasons" questions are off topic?
I'll borrow from a comment that @doppelgreener made under the question.
This question is first and foremost trying to understand why a rule exists. It is asking about the designers' own statements secondarily to that; their statements are tangential to the rule's function.
This is the kind of question where both experience and expertise can provide an answer. Granted, I don't think it fits into the "what problem are you trying to solve" category, but it certainly fits into our "History of Gaming" broad category as it establised a precedent for at least one other game system.
Let's face it: there's damned little expertise available (in particular after folks like RSConley, ExTSR and a few others who have been around that long stopped visiting) on this site, for how interrelated the OD&D, AD&D 1e, and BECMI rules are. A veritable Gordian knot to try and unpack unless you were around first hand (at TSR, like ExTSR was) or second hand (as I and a lot of old fart were as we consumed the products as they came out).
I thus offered an answer, though I believe the the 'history of gaming' tag may be the better choice.
Most of what was published in OD&D was never explained. Or, if it was, one had to soak it in as Dragon/Strat Review articles came out. While some restrospective "here's why we did that" is available on places like dragonfoot forums, it's not comprehensive.
As the later OD&D derived systems came out, particularly Gary's Magnum Opus, AD&D (1e), some stuff got a fuller explanation (usually in the DMG) on what was behind it. And some never did.
I'll add to may answer once I dig into a few other blogs among the D&D/RPG archeologists, but the evidence in the AD&D 1e PHB seems to me to explain what was going on when EGG put that terse bonus into the original book: which was tightly constrained by space, and which got ported into BECMI.
What is in BECMI - cited in the question - could easily be explained by @ExTSR, who wrote it, but he stopped feeling welcome here a while back. (Separate topic, and water under the bridge if my last discussion with mxy on that topic is any indication).
I think the question's fine and on topic.
The person has a concrete problem they're focused on: they've identified a rule, and they don't understand the function of the rule such that it exists. They're asking us, the experts, to explain what this rule is here to do. And the experts have answered, outlining for us the practical problem that occurs in gameplay in the absence of this rule that its existence addresses.
In our FAQ for asking about designer intent, we're directed to a different way to ask questions about intent: “What impact will it have on the game if this rule is changed in this way?” Well, this question's functionally asking this: what impact would it have on the game if the rule was gone, and thus, why is it there? It worked well and received good answers.
Yes, the question also prompts for designer explanations. I believe this is an entirely secondary, tangential prompt as one potential angle for seeking an answer to their primary question, which remains: what's this rule here for? That follow-up question doesn't need to be there because it's not remotely core to the question and is getting it targeted for closure incorrectly, and it was in fact removed a short while after this meta question was opened (based on conversation in chat) but has since been put back.
What I don't get is why that secondary question is what we're looking at so intently. Earlier today we received another question: How do you teach someone else how to play D&D?. It was asking how to introduce someone to D&D. It did so by asking what videos or so on we should show the player. This would get it closed for resource recommendation. We can tell plainly however this is not the main thrust of the question or the person's problem—they just want to introduce someone to the game. So I updated the question to ask that part out loud:
I want to teach this person a basic grasp of the game, and let the rest of us fill in gaps as they come up. How can I teach them this? Are there any helpful resources, online guides, videos I ought to give this person for example?
The question's open, doing well, and has received several good answers guiding this person on introducing a new player to the game. We didn't close it as a resource recommendation, and still haven't, despite the fact it includes a request for resource recommendations, because we can tell it's a good clear on-topic question and the resource recommendation is entirely secondary. (I didn't make this edit to sneakily make a point, either, to be clear—I just made this edit because it's what the question needed, and now hours later while writing this answer noticed the parallel.)
I think in closing Why do characters with a high prime requisite gain bonus XP? as a designer reasons question we're doing ourselves a disservice. It's clearly worked well, and there's something for us to learn about how this question got structured such that it worked. There's no problem we're solving in closing it. I don't think closing it is following the spirit or the letter of the law in any fashion, it's just ... a perfectly fine question. Leave it open.
If we look at the revisions to the post we can see that up until the most recent revision, the question explicitly asked for designer reasons:
Did the game's designers ever explain it, either officially or anecdotally?
ThomasMarkov, with zero input from the original author (who has not logged into this site in over 5 years), removed this line, and then started this meta question about whether the question under discussion is a designer reasons question.
The complicated history of the D&D versions involved has no bearing because the asker explicitly asked for designer reasons. If the asker had explicitly asked for the history of this rule, or if there was any lore associated with it, then that would not be a designer reasons question. They didn't ask that, they asked why the designers made that rule.
