With 4K, you can get 3840×2160 image, which is four times the resolution of Full-HD.
Meaning no disrespect, I believe you're missing some things about photography. My G3 takes 4160x2340 images, and at 13MP that's 2/3 the size of a standard dSLR image. Canon's current Rebel dSLR shoots 6000x4000 images.
Then we get to talk about optics. Would you rather a $15k video camera with no macro capability, or a $25 lens that will shoot images equal to any you see here? Heck, many of our members are using those $25 lenses. I do.
4k is amazing for video, but it lags still photography by a decade.
And that detail crop above is of terribly insufficient quality for coins.