What's it all about?

So after years of trying to get books published, I've done the only thing left to do... publish them myself. I know they sell, I've sold several already. So why do the publishers keep sending me form letters saying "not marketable"? What they are really saying is Not Guaranteed to make money! And not just money but LOTS OF MONEY. Apparently it's not about art, talent, even filling a need, it's about the almighty dollar.
Signed
A disgusted but gifted artist!