When Apple announced the iPad Pro would continue to run iPad OS, while Macs run macOS, some pundits criticized the decision. But there's a very valid reason behind it.
Why Apple Won't Unify macOS and iOS
Microsoft’s difficulty launching a lightweight Windows variant called Windows 10X is all the reason Apple needs to keep its iOS and macOS ecosystems distinct and separate. Here's why we don't expect to see a unified Apple OS any time in the near future.