The specific advantage is that it makes switching providers really hard. You develop in Atom, store the code in GitHub, use GitHub Actions for CI/CD (if that's viable, I'm not super familiar with the product), use GitHub to manage the released artifacts, and publish them to GitHub's app store.
That makes it really appealing to buy because you don't have to talk to 7 different vendors and duct tape their solutions together with Python scripts. You talk to 1 vendor, who gives you all the pieces, and the pieces are already able to communicate natively.
It makes it really appealing to sell because once you buy in, it's really hard to get back out. Imagine trying to replace all of those components, and the developer time you lose as people get used to the new systems and how they all work together. Bonus points if you can only publish to the GitHub app store from GitHub installations. GitLab can do a lot of those things, but they don't have an app store.
As others pointed out though, it would compete with Microsoft's existing app store. I would not be terribly surprised to see some kind of integration between GitHub and MS's app store, or Azure and their app store though.
Apple - Blocked
Android - Pointless without a drop in replacement for Google Services.
Windows- This is possible, but Windows doesn't really have a distribution problem. There's no real need here.
Linux - Again possible, but no real need
You have a source for that claim?
They charge said developers a few dollars a month per seat. GitHub could somehow instead be taking a 0%-20% cut topline revenue from some of the apps they host.
Lots of work to make that happen the upside might make it worth while.
I dont know what a normal person would be doing on github.
If GitHub could somehow solve the demand side (Phone users) they'd be sorted.
That light at the end of this tunnel is an oncoming train. Not freedom.
I’m not saying it’s the best thing for GitHub to do, but...
Let’s say 15% of Android top 1000 apps are sitting in private repos on GitHub. With their build tools GitHub make it possible to automatically push builds to this imaginary store, they offer devs 50% discount on whatever cut google take if on the play store.
Of course, there might be reasons form Microsoft to create an alternative to the App Stores say for a gaming marketplace etc. But specifically for GitHub I cannot see why they would be interested in the overhead.