You're making things up; who are these Linux users demanding anything?

Generally speaking once a game developer gets it working on Ubuntu the Arch wiki guys will happily figure out the rest on their own.

I thought steam only supports ubuntu and therefore games only support ubuntu. That being said, I use arch and most games just work.

Rocket League isn't available on Steam (anymore). Epic does not technically support Linux outside of Android.

Rocket League is not (yet) available on the Epic Games Store, and has not been removed from Steam.

It would require them to write it in vulkan which would improve performance across the board on both platforms...so really I think we are asking them to do a job that will cost them more money than they expected for a product they can maintain longer for less effort. You can have both but you have to know what you are doing, epic is just tending a garden that someone else made and clearly doesn't have that level of forsight.

If they release the source, every distro can figure it out on its own.

And if I had a magic flying Unicorn I wouldn't be stuck in traffic.

There's zero chance these for-profit companies are going to open source the current game that they are selling.