At least in emergency care, nurses independently resolve the vast majority of cases (though of course the doctor on duty has the final say/responsibility) and also have significant medical training. Nurses are also responsible for triaging (prioritizing) cases which is not infrequently a life and death level of responsibility. As part of their education nurses are also required to take classes which are generally considered weedout in the sciences, such as organic chemistry.

Most nurses could likely become doctors if they so chose, but 8 years of education, a few more years in residency/'bootcamp', and at many places having insane hours + being always on call, and everything else that comes with being a doctor is not everybody's cup of tea.

A nurse is much more comparable to something like a dev whereas a doctor is something closer to a combination of the tech and dev leads. QA doesn't really have an appropriate analog in medicine because every person plays a critical role. A hospital without nurses would become instantly inoperable. By contrast companies can, and have, scrapped their entire QA departments and continue to function more or less normally.

I think a key issue is that software that's overtly buggy reflects more on poor development and management practices than it does on poor QA practices.