DND_Reborn
The High Aldwin
This...What have you done with them in your games?
Kill them.
Orcs are warlike and aggressive, often (but not necessarily) evil. Any evil is perpetuated by their culture and hostile, abusive upbringing. Rarely, orcs break away from their culture, splintering off. Traditional orcs do not tolerate such acts of weakness (as they see it) and will actively seek out such individuals or groups to destroy them.
FWIW, I've never had an orc PC, but would certainly allow one if a player wanted to play it. It would face very harsh reactions from most "civilized" areas and have to work to overcome it. I have had "good" orc bands and NPCs, certainly, so the players understand such things are possible, but rare (because the orc tribes try to stop it).