A rather more plausible explanation is that people take these using their web cams.
The web cams are usually cited at the top of their monitors, perhaps pined up there.
They look at the screen while pressing the save button.
So, they appear to be looking down, but are actually looking ahead.
Have you noticed how many take a photo with their mobile phone in the middle of the frame? Chopping off half their face? Like they have to look at the screen while pressing save!
Cute.