If you watched the trailer for The Batman and thought to yourself, "Why don't you hear Nirvana in more movies?" you're in a club of at least two.
After all, to a certain generation, i.e., the people making movies right now, they're the most important band of all time. You'd think they'd pop up every time a teenage boy who looks suspiciously like the director has some kind of life-altering moment (probably listening to Nirvana).
Well, there are a few reasons: The rights to those songs are expensive, yes, but not outrageously so. Nirvana albums still sell surprisingly well, so Kurt Cobain's estate, which owns 98% of the band's music publishing rights, doesn't need the money. It's also owned by his widow and daughter, who have a reasonably high stake in making sure none of his songs become forever associated with Coca-Cola or whatever, so they're priced at "If you really want it, sure" levels.
The bigger problem is that those songs stick out like a poorly placed boom mic in any scene they're in. Think about any fictional movie or TV show you've seen that featured a Nirvana song. It was probably specifically intended to evoke nostalgia (e.g., Captain Marvel), a joke about how out-of-place it is (Pan, Moulin Rouge) ...
... or a scene that was actually set in the '90s (Definitely Maybe, Californication). There's a reason for that. How jarring would it be to hear those songs in a typical love or action scene where no one is wearing flannel? The big exception is Shoot 'Em Up, for which "Breed" was clearly written, even if Cobain had no way of knowing it at the time.
Even in the trailer for The Batman, they had to add all kinds of instruments and "orchestral flourishes" to "Something in the Way" to make it sound like something that belongs in a movie in this century, and it's by far their most versatile song, as far as that goes. They simply did too good of a job of defining an era.
Manna talks probably too much about music she was barely, if at all, alive for on Twitter.
Top image: Warner Bros. Pictures, Geffen Records