Agreed, a lot of adults don't text because they just don't want to invest the time in learning it. When you've used a phone all your life, texting can seem kind of pointless. As an Autistic, I find it has its advantages in that I don't have to keep up my end of a social interaction and know what to say in the pauses, stumble over my thoughts and then not be able to tell when or how to end the conversation. Someone who doesn't have those problems might just feel texting is more trouble than its worth, when you can just hit speedial and say it rather than bothering to type it all out.
I've also found over the years that a note can be much more easily misconstrued than a verbal statement, and people can get all bent out of shape and p*ssed off about something said in a note because they can't hear the vocal inflections that tell them HOW it was intended. Flat remarks can come off as sarcastic insults you never meant that way, so more often than not, direct communication is superior because it transmits complex subtleties that for most people printed words cannot.
And, as others have said, if you don't ask a question, why would someone feel obligated to reply? I don't answer texts if there's not a direct query, because my phone is prepaid and it costs me minutes to text, so I won't unless there's a compelling reason.