Essentially, this is one of the reasons why Rockstar aren't the same studio from the early 2000s who would publish like 2 or 3 games a year, because they're not really a publisher anymore. They're more analogous to Valve; they have more than enough money to self-publish big, AAA releases that they develop internally.
It still doesn't explain why they only make games once every 5-10 years now. Again, just like Valve.