Science often requires if no other resource extensive time and it comes to pass people out there will pay you to invest your time in it only if you are a first class member as attested to by a degree and position. Most of the people who are indeed first class end up as first class members.

Citizen scientist seems to me to denote that one is actually a scientist despite lacking credentials unlike the 5000 other crackpots. To call someone who has no credentials a scientist would be misleading thus the term has utility and meaning.