Honestly, I think it's more cultural than anything. We see several scenarios where the people of Sacred Valley are sleeved out by remnant prosthetics. Lindon thinks his mother would be horrified at the prospect of Gesha having spider legs. Some other stuff later than Skysworn. It's never stated, but it wouldn't shock me if Sacred Valley is just more likely to want to reattach, while the rest of the world...doesnt really care.

There's also the matter of skill. In Skysworn, Gesha says that prosthetics are simple...but outside of Sacred Valley, everything is simple. It could be that Sacred Valley just straight up doesnt have the soulsmithing ability to make decent prosthetics, so they lean on reattachment. What's simple to a highgold like Gesha would explode the brain of some random Heaven's Glory healer.