What evidence? If you prefer alternatives, then those are available
It’s clear why people prefer Steam: it has good features. But the other launchers should complete by making better features not forcing Steam to remove features.
Other services exist to achieve those things so it’s not necessary for them to do it
Not necessary, no but it adds value to it’s users and thus making their platform the most popular.
Like Epic’s launcher is the perfect comparison for this: It has the bare minimum features available to sell games and people hate it for it’s lack of features. It’s not necessary for Epic to add those features but clearly people value those in their choice of platform.