+Fifteen years ago, Facebook was amazing for this: everyone posted all the pictures they took at [event] and tagged everyone who was in them. But, you know... That wasn't as profitable as all the [everything else] they thought up, and they ruined the platform.

Practical suggestion: you can ask. Someone takes a picture with you in it, say "hey, you mind sending me that?" Like lots of social things it's not automatic (which, you know, Facebook was for a few years, and that was nice), and you have to "put yourself out there" a bit. Most people won't say 'no', and the thread with the photo is an opportunity for further interaction, if you want it to be.