Why do people hate the faction war?

the game’s story is focus on war why does it have to be only two faction?? why does this have to even affect the real world?? no joke there are people who take the side of each faction to the extreme.

i mean it is just a game and we can still have pvp, both the Horde and the Alliance don’t need to kill each other to just say “it’s Warcraft” the game is focus on wars, there is literally others factions.