Post 7 why not give people total control?

One thing I will never understand about game design is the seeming inability for designers to try and prevent unnecessary error and inconvenience for their players.  While there are many examples of laziness on the part of the people who work in game development (ELECTRONIC ARTS), I simply want to focus on a general feature that happens to exist in lots of games made by many different companies.  This is the ability to change your controls.

I myself wonder every time I play a game why I can't go to the options, go to controls, and simply pick which button I want to do what.  Many games have preset controller types, but many of these preset types simply switch one key, and do not give you the exact layout you might prefer.  If there simply was a custom controller type, that allowed the player to pick each function and assign it to a key, many of the errors or simply the inconvenience of having to relearn a controller layout for a game that functions exactly the same as another game would be gone.