You mean like gog?

gog is a store, PC/Mac is the platform.

Exactly. Meaning opening system doesn't reduce investments, they foster competition. In theory, people should not consider developing for pcs because they are really easy to rip off, and well, that is not what we see.

Gog was born as a bargain-bin store for products that required zero investment and were already widely pirated, it was only upsides as far as publishers were concerned. I know it's different now, but I doubt their no-drm policy is as iron-clad on new titles ar it was on old ones - it's probably left to publishers to do some traditional checks on their own, rather than using a platform sdk.