I don't need to sympathize with a character to enjoy his or her development. I want to see how he ended up leading his group to eventually twist into doing some of the really dark shit that's suggested in the game. Hell maybe he was always a sick bastard and just took the opportunity that an apocalypse brings to be a leader.
I don't either, but as a playable character, being able to empathize with that character during their development can make a big difference to the player. Video games are an interesting medium because stories told around a character means that your player will most likely view the game world through the character's point of view and empathize with them. TLoU is a perfect example of this with Joel, even siding with him in his more gruesome times later in the game.
We are already predisposed to hating this character, making it that much harder to want to play as him. I agree seeing his arc would be fantastic, but maybe not as him in particular.