Steam reached 25M concurrent users for the first time

No, 7 million concurrent users. Why does it seem low?

I thought it was in-game, but looking at https://store.steampowered.com/stats/ I see the sum of the individual max daily counts for top games is ~6M. So unless there is an extremely long tail, that must just be people who are signed in with an Active state.

I think the argument is that if you don't like Steam's 30% cut you can still sell your game on other stores like Humble Store (25% cut), Epic (12% cut which is even more attractive if your game would be paying UE4 royalties), or by selling via your own website. On some platforms, you're locked into a single option

Steam does not have a distribution monopoly in the same way that Apple does.

I am not in the anti Apple camp on its App Store policies, but the issue is not the 30% cut, but rather the 30% cut with no other distribution alternatives and how consistent Apple is in applying the 30% policy.