However, porting a game to Linux comes at a cost and unfortunately some publishers, only thinking about profits, give up on offering us native games under Linux to increase their profit margins which are already extremely high ;-(

The reason I buy native Linux games at full price but only buy Windows games at a steep discount is to pay for that support. My one wallet won't make a huge difference in the grand scheme of things, but it is putting my money where my mouth is.

FWIW, the introduction of Proton didn't decrease the proportion of games on Steam that have native builds - that was on the decline since the failure of the Steam Machines. It did kill the third-party porting market, though. The thing that will bring the proportion back up is a bigger more lucrative market, so developers won't want to risk offloading support of their game to Valve.