Gearbox Confuse Me

So here's a thing, and it's honestly got me confused. Gearbox's Steve Gibson has been talking to the London Games Festival blog about the various Gearbox projects (but mainly about Duke), and when talking about Steam he says...

[R]ight now if a guy buys a game on Games for Windows and a guy buys a game on Steam - they can't play together. If another guy bought it in a retail store, he can't play with the first two guys.

Right now we're like "Please, work together" Our big concern right now is that these silos are being built. Everybody's separating out and it's really... as a developer who just wants gamers to be able to play games together, it's frustrating right now. Things like that are hurting the PC industry for gamers.

Eh? That... what.