Why do people like to buy cosmetic items for their game avatar?

I imagine it’s because people want to support a game they enjoy playing, and buying cosmetic items of any kind is a way to do that. Plus they also get to upgrade their character/avatar.

Everyone has their own reasons of course.

Becuase they want too look cool. It is a way to express yourself. It can also be funny to look at.

Paid for cosmetics tend to get a bad press but I always think if someone wants to subsidise my free game because they want their guy to have sunglasses or whatever, that's fine by me...

Same reason people like to accessorize themselves!

Especially in social games like virtual worlds (now called metaverses, again), where the main activity is to walk (or fly) around and chat and show yourself. I worked on a virtual world called Blue Mars (build on CryEngine) over ten years ago that supported in-game developers, some of who created minigames but most of them made avatar accessories you could buy in-game. Blue Mars shut down long ago and all the developer doc I wrote on the wiki is gone but somehow there's still a page about avatar customization.

http://create.bluemars.com/wiki/index.php?title=Avatar_Customization

They want to have some unique look and have some more fun!