That's part of the view of "creative professions." People don't see why a person would do them without a passion for it. They don't generally pay well, and you don't improve at them to get paid better unless you keep doing it, including usually a lot of work that won't bring you any money. If we're talking emotional versus logical arguments, I don't see a logical argument FOR writing solely for pay. It just doesn't generally work like that. It's so much to pursue for nothing but money.