Uber has been a long-time supporter of Microsoft' efforts in mobile, despite its efforts not paying off. The ridesharing firm has had a number of apps, from web wrappers, to Windows Phone 8/8.1, and in 2015, a Universal Windows Platform (UWP) app.
As Microsoft itself no longer supports Windows 10 Mobile, dealing a blow not only to its mobile platform, but also to its UWP ambitions, other companies are following suit. Uber's support team, when asked about support by a customer, has come out and stated it no longer supports Windows (via Neowin), instead recommending that users switch to iPhone or Android:
Yes, we’re no longer supporting app on Windows. You can use Uber with the following smart devices instead:
-iPhone (iOS 7 or newer)
-Android (Jelly Bean or newer)
In addition to the comment by Uber's support team, it is clear that they're no longer as interested in the app as they once were, as the reviews complain of the app barely working, particularly with it being unable to detect the pickup location accurately.