Not sure about Desura/GOG, but Steam has a vetting process. If you're not a game developer with a following, or if your first game doesn't meet their standards, you can't get onto their marketplace.
You're also required to use their SDK and integrate some functionality into your game. Looks like with itch.io you can just upload your binaries.
Also DRM. Some (small percentage of?) players would love to play games without launching Steam. I love the no-DRM games on humble bundle.
You're also required to use their SDK and integrate some functionality into your game. Looks like with itch.io you can just upload your binaries.
Also DRM. Some (small percentage of?) players would love to play games without launching Steam. I love the no-DRM games on humble bundle.