I'm semi-quoting Yahtzee here.
Why let the players design things? There is obviously some "best" or at least "better" alternative to what they'd do, so some restriction can be good. Customization really weakens a lot of things and extends development time. I actually worked for a game company that, past a certain point, said there could be no more new animations for the protagonist because it would involve redoing the animation in each costume. For me, most attempts at characters in Saints Row 2 turned out a bit ugly, and maybe it is possible to get the right look. But I can't; that's what modellers are meant to be there for.
There are much better ways of getting the feel of a player's own persona into a game than customization.