Because not all of us are good with mouse and keyboard games. Fallout was my first real PC Game, and that was this just passed summer. I've been raised on Consoles (NES in particular)
I still have difficulty when I play Fallout more from the controls than I do the game itself :laugh:
I have the same trouble with console controls tbh.
I started on a PC but never on realtime and or fps style fights, and still prefer a less is more approach to keybindings and key use in general in games.
However the PC can be made as simple or complicated as you like in most games.
I had real trouble getting used to CoD's layout with melee, untill I assigned the knife attack to the side ( thumb ) button on my mouse.
However FO3 - NV is next to ME2 imo the simplest and easy to use key layout on pc.