One major advantage of this, as Gurman says, is that it would potentially help breathe new life into the Mac App Store, which has never seen quite the same level of success as its iOS counterpart. Developers would still have to deploy a custom Mac UI optimized for trackpad and keyboard rather than iOS’s direct touch interaction, but much of the code could then be written once for both iOS and Mac apps.
Of course—and here I’m diverging into my own speculation—if Apple decided it wanted to create a direct-touch interface on the Mac, this would help that along as well. If apps already contain UIs that are optimized for touch, that could make it easier to bring touch capabilities to the rest of the Mac. It would still require some pretty large shakeups to adapt the rest of the macOS to a touch interface, but it could point the way towards a future unified platform.
While this speculation may come to pass, my hope is that it encourages developers to improve (and in some cases implement) better keyboard support in apps.
If this helps Apple come up with pointing device support like the trackpad (or mouse), that would be huge for professionals. I think this is a highly unlikely outcome, but one can hope.