This is phone vs phone, PS would be useless on a screen this size, as for productivity on an iPad without mouse, file system, true multitasking, support for 3rd party accessories etc it's more like a proof of concept than an actual productivity pc replacement and it will stay that way as long as Macs exist. Apple wants you to buy both at the end.
It’s also OS vs OS and ecosystem vs ecosystem. And iOS is way ahead when it comes to Apps that can utilize a modern SoC.
Photoshop will absolutely come to iPhone. Not because people would actually want to do their primary work on an iPhone (you wouldn’t), but because you could make those last minute changes clients are always requesting without having to be at a computer.
But this is about more than Photoshop. It’s about the fact Android tablets are both garbage AND dead. Google has all but abandoned them, there’s no more “tablet optimized” section in the Play Store (which was empty when it did exist), none of the OEMs bother making high-end tablets and developers aren’t bringing any useful Apps to them.
Meanwhile on the iOS side Apple makes actual performance oriented iPads along with specialized X versions of their processors with substantially more power than the iPhone versions. They’ve also made significant upgrades to iOS for the iPad. This, in turn, has driven development of even better Apps.
And this is how the computer industry has always worked. Developers always push the envelope with features that stress CPUs and GPUs while manufacturers of those keep coming out with faster and faster versions. And the cycle continues.
At least on iOS it does. The iPad is like a bridge. An App (or feature) that was once on a Mac comes to the iPad and then to the iPhone. Everything trickles down. Just like features such as video editing required $100K workstations, then came to your home PC and can now be done on your phone.
There’s no equivalent “bridge” on the Android side. If their tablet market wasn’t so pitiful you’d likely see the same development pattern happen there as well.