nKPro put Kunos on the map, the five or so years it was available built their fan base into what it is today. When Kunos announced AC they hyped the hell out of it via facebook, twitter, blogs, etc. With or without Steam they would have sold a similar amount of copies. Also, feel free to link that interview with Marcos. I assume the echo chamber he is referring to has little to do with digital delivery and everything to do with making a less realistic sim when it seems everyone was asking for the opposite. Focusing on the "hardcore" vocal sim minority is a slow path to minimal wealth. Thank goodness rF2 isn't all about the money. Back to the point, having options are great and SteamOS will probably be a hit. If I was ISI I'd have one dev looking into it a couple hours per week, just to size how much effort it would be.
Not true. If you read AC Steam forums you quickly notice that there are lots of players that first heard of the game when they saw it on Steam. That is the case with other games in Steam as well.
A lot of people don't consider that a game exists if it's not in the Steam store, just a sad reality.