Originally posted by another user
"Being on Steam limits a lot of what we’re allowed to do with the game, and how we’re allowed to talk to our users," Persson said. "We wouldn’t be able to, say, sell capes or have a map marketplace on minecraft.net that works with Steam customers in a way that keeps Valve happy. It would effectively split the Minecraft community into two parts, where only some of the players can access all of the weird content we want to add to the game."