Microsoft has stopped developing new features for the touch-friendly Office Mobile apps for Windows 10, reports the Verge.

Word Mobile, Excel Mobile, and PowerPoint Mobile first made their debut with Windows 8.1. Their significance is twofold: they have a user interface that's designed to be touch-friendly, and they're built using Microsoft's modern UWP (Universal Windows Platform) framework. They've been regularly updated since their introduction, but no longer. The use of UWP meant that the same app core could be used on both desktop Windows and Windows 10 Mobile, but with Windows 10 Mobile no longer a going concern, this compatibility is no longer a priority.

In a statement to the Verge, Microsoft said, "We are currently prioritizing development for the iOS and Android versions of our apps; and on Windows, we are prioritizing Win32 and Web versions of our apps."

On the one hand, Microsoft's decision is unsurprising. The traditional Win32 desktop version of Office is the definitive, most capable version of the application. As a practical concern, Microsoft has no choice but to continue to develop this version, because it's this version that the business world has come to depend on. It's this desktop version that's seen the most new features as part of Office 365. In that context, developing a second version of Office that's also for desktop Windows is superfluous. The Mobile apps made sense when Microsoft was promoting the use of Windows on tablets and when Microsoft had a presence in the smartphone space, because the Win32 apps just weren't useful for these platforms. That no longer matters.

On the other hand, this move is not without its costs. Microsoft has been trying to get third-party developers to build UWP applications. UWP applications have some desirable features: they're safer (because they're run in sandboxes and have a phone-like security model governing their access to files, cameras, GPS, and similar sensitive capabilities), they play better with power management capabilities (the operating system has greater ability to suspend them or terminate them to free memory), and certain parts of the UWP APIs are meaningfully more modern. In general, UWP applications should play much better with high-resolution screens, for example.

But UWP applications have had some big drawbacks: they only run on Windows 10, and in broad terms they required rewriting applications from scratch. The former issue is becoming less significant as Windows 10's market share grows, and the latter issue has been addressed in part by Microsoft's "desktop bridge," which provides a way to piecemeal migrate a Win32 application to UWP, but nonetheless these factors have limited UWP's appeal. If Windows 10 Mobile were on several hundred million smartphones then the price might be worth paying, but it isn't right now. That leads developers to make the same choices that Microsoft has—stick with Win32. With Microsoft now implicitly endorsing this path, it's hard to imagine UWP adoption to increase any time soon.

The move is also a bit surprising because Microsoft has very recently shown new hardware that uses the UWP Office apps. The company demoed its Surface Hub 2 systems this week, and one part of that demo included the use of the UWP Office apps. Surface Hub 2 is, after all, touch-based hardware, making the touch apps a better fit. The current Surface Hub cannot run traditional Win32 apps, requiring UWPs instead, and the features that make UWPs better behaved and more tightly controlled would seem valuable on appliance-like hardware like the Surface Hub.