Yes, I know, chicken and egg - but most games I play don't really work on Linux and are not on Steam anyway. I'm just saying it's a dumb idea to go off usage numbers of Linux steam users. FWIW, I have it installed on a laptop, so if they do some sort of flagging, my account has repeatedly logged in from Linux and started games - just not many and not often.
This is what the AAA publishers/studios think, because mostly they make games just for the money.
They don't really care for their customers and DRM usually doesn't work in Wine and hence 'the game doesn't work'.
The indie game dev crowd, with much less resources, certainly doesn't seem to have any problems (ideological or technical) with Linux releases.
Those indie devs hardly do any support and QA testing at scale.
Many do gamedev just for the sake of the art.
It's just excuses if a $100 million project can't deliver what a couple of people without any real budget can.
But again: they want your money and it is not going to the actual developers and artists. At least, most of it isn't.
Walking the corridors of GDC(E), PAX seldom turns into discussions about OS and 3D APIs, rather business opportunies, publishing contracts, turning ideas into contracts.
Street musicians and art fair artists also do stuff big labels and architure societies don't care about.