Sure, but what does that do about players' ability to become engaged with other players' characters? To care about what happens to them?
What the PCs think or feel is completely up to the players. I ask that the players don't make lone wolves or evil PCs, but beyond that they can do what they want.
Much harder to do this with D&D and similar games than it is with others, for sure.
There's always the risk of contradicting something... we've all done that at times. I don't think the risk is greater when you haven't determined it all ahead of time... in fact, the risk is far lesser.
I have decades of lore. I don't remember the last time I had a major contradiction because I have a written history and notes of the things that may matter. Of course if I did screw up, it's unlikely anyone would notice.
I mean, if the players forget things, then no harm to contradict it, right? The point of whatever detail is to enable play.
Fair enough, but I think it's clear that almost everything you're proposing is your preference, and not what's "needed".
Isn't that what everyone who supports D&D side of thing have said? That the way they run their game is based on preference and what works for them and their group?
Why not let the player decide? If someone later wants to play a dwarf, they know what they're like... they can decide to play one or not. How is this different than if the GM decides? Or, maybe there's more than one type of dwarf, or more than one dwarf culture... again, if you don't commit to this stuff all before play, then you can allow these things to come up in response to the evolving game.
I'm with @Lanefan on this one. I want consistency in the world, there's a history and relationships between the different groups. Group A doesn't trust group B because of what someone from group B did 200 years ago is common in history. It's going to be even more common when some of the members of that society may still be around.
I think murder hoboes tend to not have connections to the world at all. At least, not any that will matter in play. As for the advantages or disadvantages of background... I don't think you need to be so alarmed about abuse. You've never had a character of noble rank? Or from a wealthy family? As I said, any advantages that brings can be paired with a disadvantage so that it's a mixed blessing.
Not just murderhoboes though. Some people are paranoid that the only reason I want them to create a family is so I can kidnap their sibling even though plot hooks involving relatives are quite rare in my campaign. Of course I just tell people that if they don't include a history I'll make it up for them.

Not at all. How does "hot jungles of the south" limit the player more than a specific jungle with specific concepts attached to it?
I'm not talking about an AP type game, necessarily, it was just an example of a game with pre-gens who had minimal world details, as offered by @S'mon ; I don't think your assessment that the designers failed is accurate because either, as you say, those details don't matter to the play offered by that product, or because they leave it up to the group to decide.
Personally I prefer broad outlines with a decent amount of gaps. Even though I've run campaigns in the same world, there's still a lot of gaps. Admittedly a lot of that is because of historical changes i.e. I don't care about city X because it no longer exists. If I get bored with my current campaign world, we can just move the campaign locale or advance the timeline. But it's still the same world, there are still NPCs that show up from previous campaigns (elves live for hundreds of years, some are effectively immortal) and it's kind of a fun callback when that happens. In addition, much of the history of the world is shaped by previous campaigns and previous PCs. So people know they can leave a lasting imprint on the world, even if they're no longer part of that campaign. That sense of history is part of what I, and my players, enjoy.