I'm willing to wager a bet the former reason is the bigger reason. Many of the data migrations I've helped with, been to services that owners know are slightly worse or doesn't have one feature they ideally should have had, but because of the first reason, it's more important to move now than to wait for it to be perfect. I don't think many are migrating because of "enshittification of services", I haven't heard that as a reason myself at least.