Most entrepreneurs are not wealthy. The vast majority of them are people who open small businesses to see if they can make a go of being one's own boss. And the vast majority of businesses are quite small. The line between small business and artisan is a very hard one to draw.

That said, I don't know why there aren't songs about it, or maybe there are and I just don't know about them. Folktales about entreprenuership could easily include "The Little Tailor, or Seven at one Blow" and "Puss in Boots". How about Pecos Bill?