I haven't bothered to see if anyone else has put this theory forth so here goes.
Today, there was some article on how the meaning of literally had been co-opted in recent slang. This got me to thinking - why do we say literally all of them were delicious or literally everyone was there. What's wrong with all or everyone?
I think that Gens X and Y are part of a language movement towards exaggeration. So much has happened in the last forty years in the US, in the World, in technology - we are overwhelmed by possibilities. In such a world, where a human ear can be grown on the back of a mouse, how can we make sure our words have enough emphasis? We exaggerate.
I do this all the time - subconsciously. If there were three of something I'm describing, five comes out of my mouth. If there were in actuality ten thousand, I'll say millions. Maybe I started it as a way to make what I was saying more interesting. Maybe it's a self-inflicted impostor syndrome defect. I don't know. But I do it. I try to catch myself, but it's such a habit that I don't always catch the words before they spring forth.
It seems to me that literally everyone in Gen Y does this. Maybe not all Gen X'ers, but we definitely planted the seeds with Valley Girl slang (totally! awesome!) and now we reap what we sowed. Why say something was amazing when you can say it was literally the best thing ever. Isn't that more fun? And who cares if it's not true - some new amazing thing will come tomorrow that we can honestly label as literally the best thing ever.