I really like this idea by Andrew Ambrosino for bringing UIKit to the Mac.

Not only would many third party apps come to the Mac, but Apple apps that have been only available on iOS could make the jump, like News and Health. For years, Apple has lived by the “Back to the Mac” strategy, but UIKit for macOS would allow the platforms to grow together. However, it would not at all decrease the power available to pro apps, one bit.

His example mockups are pretty compelling. The difficulty of building native Mac apps, at least relative to iOS, is a big reason why the platform does not have the exciting software developments that the iPhone does. It’s not the only reason, to be sure, but it is significant. I think this wall is one reason why desktop users are targeted with browser based apps, with all the benefits and drawbacks inherent in web technologies. Many native apps I use every day are simply native wrappers around web applications. Slack and Basecamp’s new Mac app come to mind. Even text editors, like Atom, use web technologies to render their UI. Bringing UIKit, or something similar, to the Mac would go a long way to encouraging developers to make Mac versions of the apps they are building (on Macs!) every day.

Mac iOS Development