"It really hasn't. Also, these are some reasons why it has." It is literally their whole spiel and what keeps them on the radar, even if the popularity of the platform isn't what it used to. Which makes sense, since they don't actively advertise or force their platform but they've also been subject to negative press such as their handling of the Devotion devs and "many gamers"in their efforts to prioritize the success of Cyberpunk 2077 over any potential fallout in the region.
You run on an ideological platform, you lose people on ideological grounds, like incorporating titles and forms of DRM into the storefront. Indies can default to whatever storefront they want, that's should be the norm. Mohjang did it to great success.
Being effectively forced to do it on Steam, that's basically a statement about their effective monopoly. Your accumulated Steam library is basically an ever increasing sunk cost fallacy, although to the credit of Valve they haven't acted like massive dickheads (yet). But that will change with time because the people who lead companies change over time whether they would have wanted it or not.