Both of you generalized from anecdotes.
We aren't photographers, we just goof around, and our almost-teenaged son doesn't factor into those numbers.
The sheer volume of data created is just .. it's nuts. And there's another 300gb of data generated from all the metadata, sidecar, smart search, face detection! Imagine all that plus much more that Apple Intelligence generates.
Long gone are the days of just putting JPGs into a folder!
If I was betting, most people likely pay for a cloud storage solution and don’t use the majority of their device storage.