I get I am not the average gamer, but even if I find a game on Steam, I tend to check their website too.
Specially for games I like, I try getting the GoG version despite Steam providing regional pricing, which tends to be 0.2x

Now if any of Steam’s contracts is preventing GoG or others from providing regional pricing, that’s a point worth considering.
But Steam is providing a much better game finding experience than Epic and others (although GoG seems to be doing well too, recently), so despite me not being affected by the network effect, I do see some value in Steam.

From what I see, Steam does give value to gamers. Whether it’s 30% of the game’s price or lesser, depends upon information that I don’t know.