I don't like Valve. I don't like the non-ownership model of game distribution.

Users aren't captured at all, since none of them need to purchase video games. Game developers may be captured by Valve, but game developers aren't producing anything of importance.

I'm for legal restrictions on industry practice that are predatory towards the users, but there's no need to protect the industry itself from control by Valve, since nothing important is being controlled.

Valve also can't control the gaming industry if they don't control the OS gamers use. They may be trying to control the OS, but they haven't done it yet. Until then, they can't prevent users from installing games outside of Steam. If Developers are locked in to Steam, it's because users buy games in Steam and refuse to buy games outside of Steam. The users behave this way because Steam provides lots of value to them.

If Steam starts to abuse users instead of serving them, there's nothing stopping them from purchasing games some other way.