I know this was from a bit a ago, but with how fast touch ID works you only get to see it move for like .2 seconds unless the very rare time it doesn't read our greasy fingers and you get to watch it as you try again.While I agree it would be nice to have, problem is it would eat up battery/resources every time the screen lights up. I am sure they can enable that feature via software at some point and add an option to enable/disable it but it's only available via 3D touch right now.
I had the touch wallpaper "live" gimmick on for about two days until I figured "why have a still photo that I have to spend longer on my phone to watch cycle through a cool looking smoke cloud or whatever". then I changed it to one of my personal photos.