Why should they have a distribution platform? Pretty much every game except Gears of War had a Windows release, and at least I never considered a digital distribution platform as a kid since boxed games worked just fine. I didn't have a Steam account until Steam came to Linux, yet I played plenty of PC games in the meantime on both Windows and Linux. I bought a mixture of boxed games and online downloads, I didn't need a launcher to do that for me.

Yes, they missed the boat, but it wasn't obvious that the boat was going where they wanted to go. Valve took that risk and won big, but other large studios didn't and were absolutely fine focusing on game dev, and it wasn't until recently that they wanted in.