I have to disagree with you there.
Most smartphone users (whether iPhone, Android, or any other) are completely abstracted from caring about any kind of filesystem shenanigans such as file names. It just doesn't matter.
Most phone systems (and, indeed, desktop systems too), instead use a catalog approach (e.g. Photos.app) and use metadata (such as image details, location, date/time, facial recognition profiles, etc., etc.) to manage the library. You simply cannot create a filename that reflects all these options, and therefore using indexed metadata is the (current de facto) way to go.
Now while you might prefer to name your photos specifically with the date and time (and that's your option), someone else might prefer location. Maybe I want my photos sorted by who's in them, or my cat, or any other of the millions of ways to slice and dice photos beyond a single entity filename.
How are you going to identify all your cat photos? or your kid's school performance photos by filename alone?
The fact is that you can name the files anything you want on the disk - and you have that option when you take any image out of the Photos library - but there is not one 'standard'/default that is going to work for everyone.