Usable and capable compared to what?

There is some stuff but it is always way inferior to anything on comparable platforms. That isn't obvious for MacOS, but certainly for iOS. Not that I am a huge fan of Android. It has a lot of similar problems.

But I cannot understand enthusiasm for Apple while it restricts access to almost any part of their software environment.

Compared to pretty much anything - honestly. Pythonista is the gold standard. It has a fully feature integrated syntax highlighting editor, a built-in GUI form designer, graphics and media libraries for games, an integrated debugger, custom keyboard, a selection of Python third party modules such as scipy and Matplotlib, all the standard Python docs and tutorials and included module docs, full integration with share sheets, notifications, widgets, it's a universal app for iPhone and iPad, it integrates with the Github client apps such as Working Copy and it has built-in iCloud syncing for script folders. You can get Dropbox and Github Gist sync scripts pretty easily, I used to use an FTP server script a lot before iCloud integration came along. It's hard to imagine what else it could really need.

But let's compare it to the other major phone and tablet OS for a start. You even say so yourself. The dev apps for iOS are streets ahead of anything on Android. You seem to be arguing that in theory Apple's policies _should_ be holding iOS dev apps back compared to Android, but in reality that just isn't happening, even slightly.

I can certainly sympathise. About 6 or 7 years ago I was seriously considering getting an Android tablet because I expected the on-device dev story there to pull well ahead of iOS in the near future and wanted to be able to take advantage of that. What actually happened was I started using Codea, and when Pythonista came along I switched to that, and nothing comparable on Android ever materialised.

War story - I had to do a programming exercise for a job interview. I did most of it on my iPad on the train, including a custom compression exercise that involved writing my own bit-twiddling routines and a server remote control script using Paramiko, which of course Pythonista includes. I was remote controlling some Linux VMs running on my Mac in Virtualbox, using ssh from Python scripts directly from my iPhone!

It's a terrible shame and I don't understand why Android is so far behind on this. I suspect it's because the Open Source and Free Software communities have never really embraced Android and spent the time and effort to tool it up. Meanwhile Apple has been paying very close attention to this area and judiciously relaxing their rules in consultation with dev app authors. Whatever the reasons though, if you want to write scripts locally on a phone or tablet, iOS is clearly the way to go right now and that doesn't look like it's going to change any time soon.

I don't even have to try hard. I use a linux shell on a blackberry android phone (over 6in screen, so i call it a tablet), with a real keyboard, and it is years ahead of anything you describe.