Inform yourself what Steam Linux Runtime is before making such comments. You are 100% wrong.
If a game depends on an API and this API gets discontinued, without adaptation it will have problems. That's true for any software and any system. As a compatibility layer, Proton can keep old games compatible despite the system changes when it translates the API calls that the games depend on to what the base system has to offer. (I'm not talking necessarily of a game running on Steam in this case)
So, enlighten me, where am I wrong?
Yes Linux users generate great reports because they care and usually are more knowledgeable.
But treat the reports cost time and work, and usually this problems will not happen for the majority of their use base.
So, as the company, you can have 0.1% of your sales generating 20% of extra work that will not benefit 99.9% of the users. It is easier and cheaper to cut that group (us Linux users) instead of support.