People who didn’t have computers before smartphones came around, don’t have computers now. For a lot of people the phone will be the first and only computer they use. As for convergence, yes, it’s happening. A modern smartphone is powerful enough tu run a desktop OS. That would be good enough for most tasks of most people. Google are working to bring that to the Pixels, Samsung had Dex for a long time. But again, that will only be relevant for people who want to use computers.