Much less frequent, but still around here and there. It seems increasingly common for movies to be based on a book rather than the other way around because Hollywood is so IP crazy. Even Oppenheimer was based on a particular biography of the man.

Off the top of my head I can say that the recent Godzilla films got novelizations (apparently you can even preorder the novelization of the upcoming Godzilla vs Kong 2), but you’re right in thinking it’s rarer than it once was since I can’t think of any others right now.

Before the 15th century I’m not sure there would have even been sufficient leisure time to have a hobby