It is not enough to just come up with a good idea. Far from everyone can successfully monetize it.
One of the creators of Fallout, Tim Cain, periodically releases blogs on various topics. Recently, he decided to explain why he is not creating new franchises.
I love developing games, so it is really unclear to people why I don't make new franchises [IP]. Other people have made much more money from the IPs I created than I ever received myself. And not "a little," but much more... People who just work in a team with franchises I made many years ago earn more money than I received for creating those IPs.
Tim Cain admitted that there might be a way to solve the financial issue, but "he is not good at it" because he is simply a "good artist."
And overall, the creator is satisfied with his work:
If you are really interested in what I want — I am still making video games, and I love them, and they make me happy. I am tired of enriching [other] people through my own creations. Can you give me a reason, other than very selfish ones, like you "want something new," or "other people want to make even more money" — why I shouldn't just continue creating what I like?
The developer would like to see a fairer distribution of profits in the gaming industry; he drew an analogy with painting: "When a painting is sold, everyone makes money."