It is not just that.
I'm sure you've heard the phrase "limitation breeds creativity". I don't personally think the pithy version is actually correct--it needs one extra word. "Good limitations breed creativity." There are good limitations and bad ones. As an example, forcing a DM to run the game with total sound-cancelling earphones on is a limitation, but not one that leads to creativity.
On the other hand, things which specify pathways of response can be exactly that. Like how, for a famous example, the original Silent Hill video game got its absolutely iconic "thick fog" horror feel. Originally, in development, there was no fog--but that meant you could see the incredibly short rendering distance of the original PlayStation. They added the fog because it both solved that problem, and heightened the horror of the experience, leaving you always second-guessing whether you were truly safe. A similar thing happened on another PS1 classic, Medal of Honor, which exploited sound rather than visuals to imply a richer world than the game could actually display. Woven into the sound are dog barks, gunshots, and soldier voices in medium distance. You can never tell for 100% certain whether those are actual dogs or guns or soldiers, or just diegetic sound to make you think there's more going on. This allows them to get away with a non-overwhelming number of enemies, keeping the pacing up and the proper feel of the combat flow, without letting the player totally relax in the confidence that they know exactly where every enemy is.
So it isn't just "that it benefits me because it's what I want to do". Rules that bind GM behavior can, in fact, actually be useful to play. They can heighten the experience for the players in various ways, and they can push the GM to be more creative, not less, if they are properly designed.
Because, as I said above, SOME limitations do not actually enhance creativity and I'll be the first to bat for that. (I've said as much in many previous threads.) But well-constructed limitations do in fact foster and encourage creativity. This is one (of several) reasons why Dungeon World and other PbtA games discourage merely exploratory rewriting of their core rules without testing. The rules really have been very, very carefully thought out, designed, and rigorously tested. Changing them is a big deal and is much more liable to cause problems rather than solving them.
(Note that this is not the same as writing new player-facing moves you feel like writing--that's not only fine, the book explicitly talks about ways to do it and gives examples of well-constructed moves, poorly-constructed moves, how to turn the latter into the former, and IIRC some of their own experiences with flawed constructions they replaced with better versions. Further, it's not about writing DM-facing moves for monsters and locations. You're explicitly supposed to do that. This is about fundamentally rewriting important parts of the game itself, like the Agendas, Principles, rolling mechanic, or baseline moves like Defy Danger or Discern Realities.)