Well, a powerbank would require an additional USB cable to be plugged in constantly, which isn’t practical at all.
And it can fall, killing the port. Didn’t happen to me, but happened to some of my friends.
A dropped phone, even in a case, can sustain damage or fall in water, or even fall in a sewer…
I would be sad if my light dropped, but my phone that is much more expensive and has a lot of data? I’d be extremely worried and anxious.
Phones have a lot of glare due to having a flashlight, which can be detrimental when you want to do work with other people, and the unfocused beam makes it hard to have a significant amount of light close by.
That was in relation to the phone. If your phone’s battery pack is dead, even a powerbank won’t be able to recharge it instantly, and you’ll be left without light.
The main reasons phones will never replace flashlights are because of physics.
If we could fit a 1mm2 95CRI LED consuming 1W of power, and outputting 1000 lumens with a tiny lens, then maybe most of us wouldn’t need, or even want a flashlight.
For now however, flashlights will never be replaced by a phone’s light by a long shot.