This simply isn't true. Am an artist, and I care a lot about having food and a roof over my head.
And in general, artists of yesteryear were either already rich - rich enough so they had the leisure time to make art and the money to afford the supplies - or you were painting because a person with more riches than you have paid you to paint (and you probably weren't poor to begin with).
Folks weren't really painting monarchs out of love for the monarch, they did it because monarchs and other rich folks paid, sometimes handsomely. And you were paid to paint them in the best light possible while still knowing it was them: The Habsburgs had portraits that were likely much prettier than their actual likenesses - comparable to photoshop and other touch-ups today.
And just to drive this in: Painters of yesteryear often had ready-made backgrounds and bodies waiting for a head/likeness and other details. Nothing says "I care more about beauty than money" like prefab portrait blanks, I guess.