Is this still the case? I have a "Files" app on my iPhone that shows me files and folders stored on my device, I can save/load files from most apps (that have a concept of files) and it's even integrated with iCloud so when I save a file to my phone's Downloads, I can access it from my Mac (and vice-versa).

I don't know about Android but on iOS I feel like we've had a simple and ubiquitous user-facing file system for a while. I use it all the time.

I suppose it might not be top of mind for most users because it wasn't there for so long.