It isn't fair to call them illiterate any more than it would be illiterate for me to not understand all the intricacies of real estate law. At some point, we as technologists gave them this communications tool without actually engaging with them in its proper use, and they learned the lowest common denominator etiquette.

When my teenage kids text me, I make sure that they use complete sentences. I'm a bit of a bastard that way, but hopefully they'll be better off later on in life.