Because they're different approaches. I would expect the "shitty" fork to be able to run Android apps, something that WP wasn't able to do, so developers had to support yet another platform for little gain.
If MS forked Android, made it snappy while keeping it compatible with existing apps, and if they did their marketing correctly I could see this carving a small but profitable (for some value of profitable) niche.
>If MS forked Android, made it snappy while keeping it compatible with existing apps [...]
That's assuming Google has some interest in not making it as snappy as it could be. I don't see what the reason for that might be.
I rather think we're talking about trade-offs here, the prime one being breadth of app selection vs quality of apps.
But any new Android fork would have to prioritise breadth of app selection as that would be the first question buyers would ask. Can I still run all my apps?
... which would realistically mean including the play store, which would mean having to pass google's requirements, which would mean relatively few modifications, no own store (i think), and including google apps.
doesn't seem like something ms would really like to do (interesting bit: they once shipped a version of android themed to look like windows mobile).
I think Microsoft is one of very few companies (perhaps even the only one) that could actually replace all the google apps and run its own store.
If they cut the revenue share to, say, 10% (or a fixed fee + 5%), then it wouldn't take long until all Android apps are available on the Windows store as well.
I mean, just open up any Windows 10 laptop and look at the 'Market' app, it definitely has the bare essentials. The side effect being that I can download movies and shows on Netflix for offline viewing on a Windows Laptop but not on a Mac (yet, looks like they caught on to this approach - sadder when people will claim Apple thought of it first).
If MS forked Android, made it snappy while keeping it compatible with existing apps, and if they did their marketing correctly I could see this carving a small but profitable (for some value of profitable) niche.