I don't know why but I feel more comfortable jotting down quick ideas for an article on my phone than on my Mac. On the other hand, I much rather prefer writing anything long-form on a proper keyboard.
I've seen so many writers switching to an iPad as their primary device in the last few years and I think it's a great choice for the professionals and hobbyist alike. The iPad delivers the 'Focus' mode that everybody wants: a full-screen application with just text and some friction to internet connectivity on the WiFi only model if you decide to set it up that way [^1]. The only limit is the software keyboard, but with so many great external keyboards that problem is solved.
We're not there for the software though and I don't think we are going to get there anytime soon. People are going to use it to write software, hell you could do that years ago with 'Coda' for the iPad, but for anything more you really need proper multitasking and filesystem. The Files app is not enough and the limited iOS multitasking is not enough. Unless Apple really changes some of their policies regarding iOS I don't see the way it could flourish outside certain niches.
[^1]: Of course you can't use an iPad without an internet connection, but it is easier than on a Mac to turn it off while you're writing and turn it back on after. It still requires will, but that's not a problem for me.