The vaccine increases immunity even for people who have already been infected. It makes total sense to have them get vaccinated.
Any risk is stupid if you already have better immunity than taking the vaccine. Once again, other diseases are handled exactly like this. Vaccine if you haven't had it, and no vaccine if you have. Doctors recognize that adding risk is a bad idea.
The goal isn't to have everyone reach a specific level of immunity. It's to get the highest possible level of immunity that is possible without taking on additional risks.