Ultimately, selling out and compromise has come to mean "screen adaptation". Even the most edgy, dark, cartoonists come to be seduced by the seductive, glamorous, high-powered, wealthy light of TV and film and sometimes internet.
Ultimately, the cartoonists with the most underground and artistic credibility these days are those who refuse to adapt their work to the production contract of an L.A. studio for TV or film. What Bill Watterson did and what Dave Sim did are ultimately harder to do and preserve (the ideology of non-financial integrity) than what artists like Todd McFarlane or Jhonen Vasquez or Peter Laird and Frank Miller did. Which is ultimately adaptation to the screen. It's a power thing. Adapting your work gives you more social and or economic power than keeping your integrity. The reason adaptation is hard to resist is because it is a guaranteed ticket for fame and fortune. It's a drug that's hard to say no to because it makes it a guaranteed ticket to survival for the creator