That’s what I’m saying. Because there is essentially little “profit-motive” to writing further books, in that they are both “on top of the game” (though Rothfuss is slipping down it, slowly), international darlings in their genre and a bit beyond, and clearly well-off enough that they’re not worried about that (which is nice, great even, but still has an impact), they’re content to sit around and fiddle with their books rather than put stuff out.
And just look at the books.
In both cases, we could argue that, the more famous they got, the weaker their writing seems to have become. I mean, yes, with Rothfuss we have a tiny sample set, but contrast the writing of The Name of the Wind to Wise Man’s Fear - there’s a distinct trend towards the self-indulgent, even the slightly ludicrous (well, more than slightly), and whilst it’s possible that’s part of a tall tale the unreliable main character is telling, even if we ignore that, then the story is just nowhere near as sharp or impactful, emotionally, and contains a lot more material that feels like maybe it could/should have been cut or edited.
And with Martin it’s far more obvious. Books 1-3, basically the “before he was visible outside the genre” books, are tight, well-written, and tell this quite effective story. But when 3 came out, he started getting visibility outside the genre, and started being treated as more than “that guy that wrote those weird superhero novels” inside the genre, and more as a sort of second Tolkien, and I have no doubt that this contributed to his attempts to make book 4/5 great, which really, really didn’t work out, at all, even slightly. I don’t think in his case it was a “went to his head” thing, even. More the opposite, a “Oh shit I have to get it right or I will ruin this series which people are really impressed by!” combined with “I now have the means to definitely take my time on this”.
As for “other commitments and projects”, well, it brings OFFERS of other commitments, not the commitments themselves. Likewise projects - it brings opportunities, particularly financially, to do other projects, it doesn’t in any way make you go with them. I’m not saying either has “a duty” or whatever, I’m just bemoaning the fact that apparently both took the “I will fiddle with my book forever!” route instead of the “finish it and move on” route.
(There’s also the more murky issue that Martin’s earlier drafts for 4/5, and where he said the story was going seemed a lot more interesting than where it actually went - well, with a couple of exceptions, but that’s very murky and I won’t argue it.)