Artistic merit is a bunch of crap ,by itself. Do people seriously believe the great artists need no food , clothing, shelter, or companionship ? The great artists of the old days were often "kept" by wealthy princes, etc, so the idea of prostituting art is laughable. Artists , like everyone, need money. They sell their art to those who want it for whatever reason. An artist with no sales starves.
Mr. Watterson apparently decided that he had acquired sufficient money to live a life doing what he wants to do as he wants to do it. Likely his income was invested well and provides him well. I saw no reference to wife and/or progeny. Perhaps there is no one to leave it all to. That is certainly not how I would proceed in such circumstances but I certainly understand and appreciate it. By not allowing further commercialization he leaves his strip untrivialized (understanding here the inherent triviality of a comic strip)and now somewhat legendary.
At the same time, an "artist" doesn't really create a character. You might want to view his C&H work more as than of an author than an artist. He's created a number of characters, who I've come to love over the years. He's obviously put a lot of thought, work, and even love into those characters. He doesn't want to see these characters used in ways he doesn't like. Besides, it seems that he DOES have all he needs for his material purposes, the characters are his property, and I say, "more power to him."
I miss reading new adventures of Calvin and Hobbes, but even reading ones I've seen a hundred times will still bring smiles to my face. I'm happy that a man who's given me so much pleasure can do what he wants.
Mark