Which again isn't equal to quality (enough to mention some "AAA" releases which were complete trash, remember Batman: Arkham Knight fiasco?).

So again, AAA or not AAA, quality is what matters, both artistic and technical.

Today, good studios are releasing games for Linux. Such as inXile, Obsidian and others.

Nothing you said is wrong, but it doesn't change the fact that quality doesn't sell. Once a game is "good enough" it often comes down to marketing, and the studios putting out for Linux do not control a majority of the marketing dollars.

Quality sells, but it requires more effort naturally.