But not necessarily professions. The notion of "professional artist" is fairly recent. Most of the great artists, pre-20th century, had day jobs: from Chaucer (diplomat, astronomer) to Lewis Carroll (Mathematician).

And, if anything, I'd think that art not being a profession only made their art better. I mean, how much can someone who all he does is write all day can possibly have to say?

Take Asimov, for example. I wonder how interesting his science fiction would have turned out had he not been, first and foremost, an actual scientist?