I keep using a lot of text messages: I have many people with different type of chat apps, or no chat apps at all (old gen), so the only way to reach everybody is doing that instead of juggling with different services.
I don't use whatsapp, and don't have an iPhone, so no imessage. Most people don't use Telegram or Signal which I do. Not to mention a lot of geeks have their favorite way of being contacted (slack, wire, etc).
And of course all that will have change in a few years. Before you had to have facebook. When in Asia, it was lime or something else.
As soon as you have a lot diversity in your life, text messages are the only thing that works all the time, plus they are free in my country.
In fact, iMessage is basically sending text messages without the user knowing they do if the other hand is not an Apple device.
In the end, I suspect text messages will still be here in 10 years, and all people around me asking to subscribe to yet another chat service will have change 3 times (and lose their contact list in the process).