Amusingly we're getting to a point where it's easier in many cases to just target Windows than ship native binaries for Linux.

So then the question arrives: since there's going to be a native Windows binary regardless what's the point of putting in the extra effort if it works well enough?

I think compatibility layers (Wine/Proton) are very useful especially considering many developers don't want to put the effort into making a well supported Linux binary (or make something open source so it can be compiled/patched against updated system libraries), but it very well may be a snake eating its own tail situation that hampers further adoption if things are "good enough".