Complete supposition: maybe teens' exposition to memes is through non-private messengers and apps, meaning all media is saved automatically on the phone and available through a search. I don't think the web is very much used still.
Yes, and the database is useful for all the situations when you saw a meme on someone else's device, or embedded in some piece of content, so you had no way to save it.
I know the obvious response to the above will be “yes, really, teens do that. Pictures of everything”
But really? Everything?