Speaking as a millennial, millennials as an age group have a lot to do with it. Have you actually communicated in writing with people of varying age groups? It's blatantly obvious to anyone with "millennial" / "Gen Y" (loosely: born after 1985) family or friends that emoji use is heavily driven by younger users.

Further reading: http://time.com/4834112/millennials-gifs-emojis/

lol (if you'll pardon the irony of that)...

Although I grant you that plenty of baby boomers (and even older folks) do in fact use emojis, you can't seriously be arguing that they do so more than younger generations?

I would love to see some actual research on this. I have a completely untested theory, purely based on direct observation of my own friends and family, that the people who use emojis the most are those with the lowest writing skills. If that turns out to be true then emojis are in fact exacerbating the problem, because it doesn't much matter if my mother uses emojis instead of learning to spell, but I'd be very concerned if my daughter did.