Being banned from multiplayer games is no different from any other multiplayer system
Which is a moot point when talking about a
single player game. Why should I need to maintain a separate agreement for an online-based account with Valve (a third party) to play an offline game from Bethesda? An agreement that, if for any reason is broken (through my fault, Valve's, or even a fourth party), can affect my ability to play that game? If I buy a physical game through Best Buy, and I run into problems later with Best Buy, I can keep playing the games I bought through them. With Steam, I may not be able to keep playing, which is why I don't want to deal with them. Especially for games I'm going to be playing for a long, long time.
The more time goes on, the more likely a problem is to occur. I, and other people, don't want to take the chance of such a problem occuring that can irrevocably block access to games we paid good money for. You want to take that risk? Great, more power to you. Hope it works out in the long run (honestly). Just don't
force us to take those unnecessary risks.