even at that point why develop what's probably going to be a mediocre alternate stance game when you can refine and perfect your normal stance. takes a lifetime to learn one.
in MMA a lot of wrestlers stand southpaw because that is the more conventional stance in wrestling, but fighting as a converted fighter is far different than stance switching. Machida, Anderson Silva, Hagler, De La Hoya, Cotto, Andre Ward, too many Thai guys to list, a lot of guys fight with their dominant hand forward regardless of whether they are left or right handed.
but not a lot of guys master some ancient eastern art of effortlessly flowing between stances and leaving your opponents hopelessly confused. you get to a certain level and guys aren't going to go into mental shock when they see you switch, they're probably just going to beat the shit out of you as they know how to fight both orthodox and southpaw fighters and you're trying to incorporate a stance you've spent a fraction of your total gym time in.
moreover as above bro said it can be a mental crutch. "oh well i'm not doing well in this stance let me switch to the other and see if i do better" "nope not working here lemme try the other" rather than actually diagramming what's going wrong in the ring and coming up with a real adjustment.
like i said there are certain techniques where you need to switch to execute, switch kicks + kicking combinations most commonly, + Pep made a career out of circling either way and leaping in with whatever hand was back whenever he had an angle, but unless you're executing one there's very little reason to switch.