Good question. "Evil" persons in real life are frequently psychopaths who lack the necessary empathy to see other beings as beings, for them humans are just obstacles or means. Many evil deeds otherwise are results of special social circumstances and don't fit to an evil playstyle because they are not reproductable. Or evil deeds result out of ideology, like religion, fascism, communism or other -isms, where you commit terrible things (in the view of others) because of a greater good you allegedly work for. I think in the game you can be a psycho or a zealot of ideology to justify an evil playstyle.
There is also a certain admiration in some societies for a certain kind of villains, who are "so cool" and such big personalities because rules don't count for them. Remember the movie "Bonnie and Clyde"? Some disgusting real world murderers with deep psychic problems became heroes in the movie, which also used blatant lies about the policemen who killed the pair, to make the villains more sympathetic. No wonder that evil play might appeal to some in such societies.
Larian can do whatever they want, they will not get me to play an evil character. I lack the ability to roleplay something different than I would be in the gameworld. For example, as soon as I realized you cannot avoid killing guards in Red Dead Redemption 2, I deleted the game asap from my harddrive and was then annoyed about myself to have bought such a crap despite I should have known better before.
