A few things:

1. It gives manufacturers a blueprint for their devices. You will see a lot of handhelds running SteamOS from different manufacturers. You will also see a lot of small “gaming boxes” with SteamOS to plug in your TV. That’s great!
2. Game Developers will have one distribution to test their games on. One of the bigger problems linux had before SteamOS was the big clusterfuck of different distros. Great for users, but a big headache if you’re developing for it. Now you can say “it runs on SteamOS”, test on SteamOS and you don’t have to deal with bug reports from people running RedStarOS
3. It’s Valve. It’s a company. They are the biggest store selling games and they are building their moat to protect themselves against Microsoft, Apple, Epic & Co. That not exactly great for users, but also explains why Valve is doing this linux push. To prevent Microsoft from abusing their Windows monopoly to crush them

You should remove old posts & comments from every site you post to on a regular basis. There is no reason for those pictures from 2007 being on Facebook. Your old Twitter comments from 2011 might bit you in the ass in a few years. Nobody in their right mind is looking at your 2014 Instagram posts and you don’t want people out of their right mind seeing those. Why should that comment about Obamas election still be available for the world? Just nuke your old stuff on a regular basis - nobody looks at it and if people are searching through your old posts, they want to harm you.