Yep, it’s fine to roleplay a character who can’t be cured, or just prefers it that way. Just as it’s also fine to have a tabaxi be a vegan, because it’s a fantasy and players are allowed to express themselves however they wish and the lore is always secondary to player enjoyment.
Even in a setting where having your head chopped off is a minor inconvenience for anyone who has 1000g, there would still be people who choose not to have an amputation healed for any number of reasons, and thay choice should be up to them.
They want them even more as middle managers.
The CEO’s goal is to be able to say “we had the best intentions, I have no idea how it went so badly”, and that requires a bunch of layers of middlemen who are willing to do anything to meet targets