I really think Valve have become the de-facto owners of the “don’t be evil” motto nowadays, even if they don’t advertise themselves as such.
It’s not just factually wrong to call them a monopoly, it’s uncharitable given that they are not engaging in anticompetitive practices despite being in a position (and arguably having the right) to do so.
Well, not quite. They did get sued for having "anticompetitive restraints on pricing" and "Federal Judge John C. Coughenour ruled that those claims were credible and that Steam gamers can claim compensation for Valve's illegal monopoly, but gamers, unlike developers, must file individual arbitrations to do so."
(Their ToS wouldn't allow gamers to form a class action, but developers were apparently allowed to.)
So, perhaps not all good.
This was in defiance of the fact that some lawyers were arranging a mass arbitration lawsuit over this stuff. So Valve is flipping the table hoping to evade that.