It's a very good question! Well because of my specific of work I have to use PC or Mac fully functional file system access. I mean iOS is really frustrating once you want to work with the files. Only clouds works more or less good there but I usually need more control on that. Another reason is yes, Photoshop is industry standard and I have to share source files with my customers often. Plus if I draw for animations or designing some characters for games or advertisings they also need to stay on separate layers and it should be interchangeable in between different machines like I share the file with customer and then get it back with some editions. In that sense Procreate is less flexible but still using some cheats it's usable. So if there would be that case when I have only iPad Pro with me I can work but still I prefer fully functional PC or Mac for that case. I wish Apple would release iPad Pro with Mac OS on board one day...