This is the thing that makes me realize the small amount of roleplaying I did growing up wasn't really indicative of "the community", such as it is. For my family and friends group who played, the sourcebooks served as inspiration, something to read to get the ball rolling. Dice were just an arbitrary mechanic to fall back on as a way to add gambling-style tension to encounters or prompt players to come up with a more creative solution. Nobody ever wants to "lose" an interactive storytelling session so getting caught up in rules feels against the spirit of the thing. And yet, here we are. I guess a lot of players take the rules and the lore a lot more seriously than we ever did.
Depends on when you played. Earlier editions of D&D were much more like this, offering guidelines with dice and otherwise just leaving it up to DM or group discretion. This usually demands more of the group and also makes it harder to stitch a wide, cohesive story together. Later editions responded to this and added more mechanics and rules to D&D.
Yeah, there's a form of D&D which is "I want to tell an interactive story and see where it goes" where the dice are basically just a way to keeping things a bit sane, and then there's "let's simulate a computer program using sheets of paper and a bunch of random number generators" which I kind of feel is where D&D went.
Us too. Though in the end we settled on the Fighting Fantasy RPG rules as they were simple enough to play in the school playground whilst also providing just a little bit of authority to decisions.