Well, in my experience, and this might be rare occurrence, but playing with fully random rolls caused me to play barbarian basically every game. I've always gotten bad stats all around, or only good strength, and so I pick barbarian to increase my stats to more tolerable levels, and to give me a higher chance of getting less abysmal hit point rolls to make up for my inevitably ~10 con. When I can pick my stats, I'm never a barbarian, and always pick something different every time. The friends I play with tend to also only ever get really bad rolls, so I see a lot of characters that don't need to rely on DCs to get things done (trying to get a spell to land on an enemy you don't know the saves of with 11 DCs is not advisable...), all magic missiles and healing focused clerics, or classes with a ton of skill points that avoid combat like the black plague. It really, really cuts down on the variety. I find that players also go very far out of their way to try to make up for their poor ability scores via min-maxing as hard as possible, and the RP suffers for it. Once again, this is just how it's happened for me, and I can see the draw of having the possibility of getting stats James got... but I have negative luck, so now I'll only run a game with random stats if EVERY player wants it (which happens) and I generally avoid being a player in them unless there is free food (which happens).