Let's see... This hospital, call it Hospital A, will pay a $10,000 signing bonus to hire RN's that are already vaccinated. The nurses already working at Hospital A that have worked long hours through the pandemic and got their vaccination don't get anything. So vaccinated nurses working at nearby Hospital B, quit and hire on at hospital A and collect the $10,000 bonus.

Then Hospital B gets desperate and offers the same $10,000 signing bonus to hire new vaccinated nurses. Then the pissed off nurses at Hospital A quit and hire on at Hospital B.

Same number of nurses working, just at different hospitals and with $10,000 extra cash. Most hospitals have a 401K type retirement plan, which is portable, so years of service at one place aren't that important.