Why do nurses/AHPs think they can give good medical advice to laymen?

It’s funny seeing how nurses and other AHPs that are not qualified doctors, act as if they know how to diagnose any sort of condition that their family/friends may encounter. They especially seem sure of their diagnosis because they “see it all the time”. Sure minor advice is fine, but many times they seem to act so assuredly, even against the advice of a qualified doctor. Any thoughts??