It's because the PC version has extra features available, like hats and costumes (I don't know if pets too) and on Android you have to pay to have these full features
Then why not make a pc version without the hats and stuff?
There are already some requests for this to be done, just enough the developers may be able to release a free version with limited features like Android and IOS. I think they did it because they still need to have a steady income to keep updating the game (although they said they won't add more maps), but this is something that can be done in the future
search among us free download for pc on a browser and you´ll find soooooooooo many like you said.