I saw Atari ST in music studios well into the late 90s/early 2000s because back then quiet beige PCs weren't a thing yet: PCs virtually all came with super noisy fans, which was a big no-no for music studios.
A buddy would bring his Korg synth to my neighbour's house and hook it to their Atari ST. Another dude I remember would play drums from Dire Straits song from his Atari ST hooked to some MIDI gear and then he'd take his guitar and play Dire Straits songs.
These were the days.
I'm not surprised some musicians still use them. If I'm not mistaken Kavinsky (who became famous after the movie Drive came out but recently had renewed interest for he performed at the Olympics games' ceremony) started doing music at a late age, on an Atari ST a friend of his game him.
As an anecdote PCs were so noisy that I asked my neighbour (an electrical engineer) if it was possible to come up with a system where the fan would slow down when the CPU wasn't too hot: and sure enough we were then modding our PSUs with "thermistors" and we'd be calibrating our tiny hack, no shit, with boiling water in the kitchen (ah clueless teenagers). Funnily enough about 10 years later every single PSU had variable fan speed.
That's the thing: we were used to quiet 8-bit and then 16-bit computers and when we had to move to these piece-of-shit PCs (but with fast CPUs / FPUs and that were upgradeable), we had to endure these painful ultra noisy CPU/PSU fans (and HDDs).
So the Atari ST just made sense. You could have these super fast (compared to Atari ST) PCs but they were noisy, fugly, piece of unbearable shits that the cool guys in music studios simply wouldn't tolerate back then.
Now of course at some point PCs became just too good and several brands started focusing on quietness and it was then possible to have a totally silent PC, both looking cool and being literally cool (big heatsink, quiet fans, etc.).
But yeah the Atari ST was and still is certainly for some a thing for creating music.
Lots of respect to the Atari ST for his MIDI port (and that comes from a Commodore Amiga owner and fan).