They probably don't. So it's up to the players to decide how they want to approach the creation of their character. Some players will start the process by examining the classes and subclasses first, and then work their way toward pairing their choice with a particular race. Other players are going to start by checking out the races and work their way toward picking a class. Like it's been mentioned earlier in this thread, there is no right or wrong way to making a character.But why should WotC care about procedural "realism" over fitting the process to actually usage by most players...?
There ought to be a poll on this.