Earlier quoted context omitted.
Because with the exception of very few tasks like digital art the limitations placed on iOS make it worse. Some tasks are just straight up impossible (e.g compiling code), others are just hampered by things like file management and sandboxing or lack of support for hardware/accessories. Sometimes they can be worked around but often it's an exercise in frustration to do something that would be brain-dead on a desktop…
All I can figure is difference in perspective is because such a large part of the potential of i-devices (or phones and tablets more broadly) for creation involves using them as a tool to get something done in the real world, and/or for the kinds of creative tasks that get overlooked by the hackerspace crowd (running an Instagram, say, involves lots of creation ; tradespeople and home DIYers routinely use phones and…
The main one for me is the longevity of your data. It is connected to the control over your data you have in a desktop OS. Good luck finding what you did five years ago in an app in some device and reproducing it now. You are at the mercy of some proprietary format the app creator chose, the availability of the app at a later stage, whether you saved your work in a cloud service, whether you kept your old device running, the operating system updates you installed, .....
With a desktop you can archive your work, whatever it might be, in sequences of bits that reside in your disk. Open source software and virtual machines go a long way for helping reproducibility.
Not all tasks benefit from reproducibility and longevity but I'd argue they include a lot more than computer programming