I don't. But not because I think my dumbphone isn't also basically a mic I carry around, but because mobile devices are a joke, one and all. It's like moving back to communicating with infant sounds after I learned how to walk, form sentences and use tools -- why would I? Because so many people do, that they already assume everybody does?
I don't need e.g. Whatsapp to stay in contact with people I care about and who care about me, if I was only reachable by mail they'd send me letters. Anyone incapable of that I would surely dislike for dozens of other reasons already, so the question of "how to stay in contact even though I don't have a smartphone" literally didn't come up once since Apple "changed the world" in 2007, heh.
This stuff is just a very recent blip in our evolution as a species, and the phase we're in is about as impressive as the lies people told each other once they invented writing. It too shall pass.