Pixelmator, a universal binary photo editing app, doesn’t have that limitation.
It starts in the room (multiple rooms probably since you have to create the assets, and test it in various browsers too), so making it portable would only be a minor convenience. In other words it’s a workflow that starts on the field why not also end it there? Why ever nail it down to your workstation if you don’t have to? Coding/animating/design is very different.
I would add that photo manipulation is a more natural fit to a portable and touch device than anything else is: Many photographers (amature and pro alike - with cameras in our phones, everybody qualifies as a photography software consumer) would want to properly retouch/manipulate the images that they just shot while on the go. Couldn’t agree with you more I’d also like to see, how AD for iPad pro fares in the market.