I find it unfortunate that the only Apple device with a screen refresh rate higher than 60hz is the iPad Pro which has "up to 120Hz".
I suspect this is due to the difficulty of most of their devices already have in reaching 60hz, which makes this situation relatively understandable.
I acquired a 170hz GSYNC compatible gaming monitor with 2k resolution recently and it has opened my eyes to how smooth interfaces can be. This is a super-premium experience, and I don't expect most users to afford or need this. But Apple has always tried to be super-premium, so why don't they have it?
When will we see their "Pro Motion" displays on Macbooks and iPhones? Probably soon, but many PC users are already moving to 144hz monitors as they become cheaper.
Graphics hardware has already caught up on laptops, but clearly not enough to allow for the slim form factor Apple seems to love so much.
Perhaps the next mobile graphics innovation is going to be better cooling (and therefore, a size reduction) rather than pure performance.
Regardless of the technological hurdle, high refresh rates make for a much smoother user experience and I hope Apple adopts Pro Motion more widely in their ecosystem.