There's probably a bit of the Photoshop Effect going on, where companies are mostly interested in having their tool become the dominant one - and the dominant s

There's probably a bit of the Photoshop Effect going on, where companies are mostly interested in having their tool become the dominant one - and the dominant skill - in the industry over piracy litigation. We're in a perfect storm of access to development tools and interest in indie development thanks in large part to Steam and Kickstarter. In the case of Valve, I think what butters their bread isn't Steam anyway, but the games people end up making with it that Valve get a cut from through Steam.