I would guess it heavily depends on the place you look.
There are more artists than game devs. Artworks are sought after outside of games and the skillset is more hands on. Game dev skills are very narrow (in the sense that they are mostly good for game development) and there are many people with no coding background creating games as a hobby. Being an exceptional single developer would include being able to do your own art. Not unsimilar to a singer songwriter that can play an instrument.
So finding an artist that works for money should be trivial. But I would not look on Itch for those. There are specialised places for that.
Finding a paid coder should be very hard, because if you have the money to pay one, you would also have the kind of money to simply start a small game studio. And commissioning a coder might be complicated than commisioning artworks. Also, I see artists proclaiming they are open for commsion, but I do not recall coders doing such.
On the other hand, Itch's special gimmick is the game jams. Finding someone to collaborate on a free hobby project might be easier than finding an artist that does it for free, if you look on Itch. https://itch.io/board/10020/help-wanted-or-offered
I suspect that not that many artists go to Itch to be found, and based on that assumption I guess those are the rarest to find, which would be in line with your feeling. People seek artists, because they themselves are game developers and hang around at that indie game developer site. Artists hang around at artist sites...
Those are my 2 cents to that question.