if there's any sort of gameplay benefit to going to one extreme or the other, which almost always seems to be the case.
I'm playing through the mass effect series right now for the first time- I go to level up, and it says I can't put any more skill points into charm unless i have more paragon points. I like playing my characters as somewhat "believable", so where does that put me? Wa.
In the star wars mmo apparently you can't wear the cool-looking armor if you're not extremely light or dark side-aligned. I don't think there was any real reason to go super light or dark in knights of the old republic, might've made combat a tiny bit easier but I didn't really care.
I just don't like the idea of being penalized for role-playing in a role-playing game. Why would they ever do that...