One thing that I think a lot of the detractors are missing here, is a sense of scale. This isn't a "small" question, that could easily be hand-waved in a campaign setting.
This question isn't covering a minor detail which will be relevant for less than an adventure (if it's relevant at all), like the brand of a fragment of duct tape on a piece of pipe.
It also isn't covering a one-time loot issue, that any good GM will balance out anyway like how many magic hats drop from a specific legendary beast, or an easily Google-able value.
It isn't covering something that players will neither know, nor care about like the weather their grandparents saw on a specific date.
The existence of reliable cars and/or ubiquitous telephones fundamentally changes a campaign setting. It changes the stories you can tell, and how you have to stage them. It is fundamentally important to how the world works, and is something that you must know in order to use the game world effectively.
As an example, watch a few horror movies set in the present day and pay attention to the cell phones. Almost every movie will explicitly deal with the phones in some way: They get forgotten, jammed, are out of service, are confiscated, get lost, etc. The stories that the horror movies are attempting to tell are fundamentally incompatible with the existence of commodity cell phones, so they need to be excluded.
Cars and phones fall into the same camp. And while it's easy to exclude a technology for a single movie, it's much harder to exclude it from an ongoing RPG campaign, which is often intended to cover weeks or months of in-game time and offers the protagonists much greater freedom.
There may be a line to be drawn for questions about the real world. This question is well above it. The real world is, effectively, an open source shared campaign setting for a broad variety of games. Why should a game like Call of Cthulu or 7th Sea get less benefit out of this site than any other?
Ultimately, the only problem I had with that particular question was that it should have been two. The advent of cars and telephones don't really have a lot to do with each other in an RPG context.