Well, I think you need to dig much deeper to understand that. Folks have funny ideas about good and evil and what it means to be them.
Good for example, is often viewed as a part time job. You can do whatever as long as you do the good thing when it matters and in an amount that weighs more than the bad you do. Evil, on the other hand, is viewed as a full time zero breaks gig. You must kick every puppy and take all candy from all babies or you are not evil.
In this dynamic, good folks are allowed breathing room to act as, well, normal people. Evil is a caricaturized idea in which you have to be an asshat all the time. Naturally, that is going to lead to a lot of dysfunctional group play in an RPG. So, GMs start to ban evil to avoid this obnoxious behavior. Then, players react by taking the next best thing which is CN. Followed by more GM banning. Now, you are lead to this new approach where folks take obviously characters of moral ambiguity and work their mental gymnastics to be a good guy who uses evil for good. Like the assassin that only kills bad guys. You cant just be a nuanced evil guy that produces good outcomes, oh no, the person is good because they are, well, they just have to be to fit the no evil only heroes assumption.
I don't see this present in other RPGs, its largely a D&D thing. So, is it chicken and egg? Did alignment permanently disfigure D&D? Or has D&D from the onset been a game intended for good with a capital G guys to conquer evil with a capital E villains?