I make a (good) living working as an iOS developer on the video editing app (LumaFusion) shown several times in today's event. We have a very solid userbase, including plenty of people using it for professional work. Apple chose to use the app as a featured example in marketing the new iPad. To me, that's all evidence that video/photo editing is indeed a "common" use case for these devices.

Anecdotally, these days my wife (an artist) does digital painting and photo editing exclusively on her iPad Pro because she prefers the software available there combined with the Apple pencil.