That has nothing to do with physical games, but with DRM
This.
And Itch already does a rather good job here. While they do not ban drm, it is so poorly supported, that you will find almost no games with drm here. There are some, but none come to mind. I see people asking for it occasionally, but it seems, it's always about games that many people would not even play if they were free.
drm hurts legitimate customers and it does not improve sales in such a way that it would recover the costs for said drm. It actually disourages people from buying, since a lot of people are aware of the drawbacks of drm. So a cost/benefit calculation is mostly wishful thinking.