Microsoft made a bet on Xamarin instead.
Also you had to use their proprietary touch events in the webview browser, which (a) was buggy, (b) had little information about how to use it in practice, and (c) the webview was a branch of IE11 specific to Windows Phone. I think for Update 1 the webview supported the Apple touch event API but it was broken (disappeared in update 2).
The dumbest thing is that supporting Cordova properly would have immediately got them a whole heap of lesser known apps without having to give money directly to developers. Money multiplier investments are smart.