Oh, I agree Most DM's shy away from it because just as people playing paladins feel they need to be jerky LG, players playing any evil character feel they MUST be backstabbing, thieving and murderous...
Seems like pre-gen PCs to me Or at least a major piece is pregen. It could definitely be fun - in past campaigns, upon PC death, I've handed players random pre-gen characters to play temporarily. Anyhow, I would never start most campaigns out this way. Player choice is what it's about.
Stretching role-playing abilities and comfort level for PCs should be in the player domain not usually in the DM domain. You can randomly select any number of statistics about a PC - it doesn't mean the individual player will attempt to roleplay them with any accuracy.