I wasn’t aware of having made repeated references to artists/collaborators who’ve moved on in that way. Commercial comics will always have new “stars,” for as long as commercial comics are around, because it’s the nature of the creature to find new blood. People have been predicting the death of the commercial form since at least the Seventies, and probably longer. The decline is of course clearly visible, and I can’t even begin to describe to you the inefficiencies and insanity that still holds in various places. But probably what you’re seeing is the cyclical changes in the conditions of production that periodically send a few people off to other media. Or, perhaps, some people simply feeling that they’ve said all they’ve got to say in that medium.
Don’t assume it’s all about money. I could have continued to make an entirely decent living in comics for some years to come.