If we end up comparing D&D to other rpgs, not all but a few, some other rpgs do emphasize backgrounds and character concepts and personalities that D&D does not, and all that is within the rules of the game itself.
D&D, from the PHB, doesn't empasize anything but number crunching, combat, and spells. It has everything to make a kickbutt combat machine, but it doesn't really address how to make a well rounded character with a background, or guidelines on how to roleplay. Sure the Description chapter is there, but its the shortest chapter in the book and all the stuff it does talk about, the most important aspects need more details (especially for newbie players that don't have any idea on what they are doing).
Sure experienced players can read between the lines and get more out of what is written, but the game itself is just a game of combat, as the rules are written.
Players do have to get beyond the rules and also figure things out for themselves, and that does take practice. The more a person plays, the more they should learn (supposedly, but I have seen players who have been playing for years not grasp the concept of a simple character concept and just how useful a single page of a background can be to flesh out a character).
By saying the above I an not going to dispute what Ranger REG said because he's absolutely correct. A DM should be able to teach a new person what roleplaying is all about, and if the DM is new then that will be a pretty hard task to accomplish. And it is up to players to get beyond the rules and understand that the rules don't dictate how the game should be played.