That’s the thing though, with their market share an hypothetical competitor could be better and people still wouldn’t switch, Steam is where their games are, it’s where their friends play, building everything from scratch elsewhere wouldn’t be worth the trouble even if the alternative was better.
Store, development, forums, trading platform, launcher, online gaming services, hardware, streaming integrated into the platform, DRM… Valve has their hands all over the place and there’s a single person at the top of that. Wanna wait until they start becoming bad before considering that maybe it’s not a good thing that they have a hold on 70% of the market? Hell, just the fact that Newell could decide that they’re closing their doors tomorrow and no one has access to their games anymore should be fucking worrying to everyone.