We all have cellphones: wife, kids, and my wife's parents<--they are in their 80s. While for safety reasons they kept the latest KRZR model for years, and it was safely in the car's console to be turned on only when they needed to make an outgoing call.
Common sense and the modern age finally convinced them to accept our offer of iPhone 6's some years ago. We spent some time showing them how to text, email, and so on. We commiserate together when Apple makes changes to the UI for No Apparent Good Reason. When he saw me use a Tide Table app to check the time for high tide, he wanted to know how he could get that, too. Despite 99.999% of the calls being from credit card/aluminum/window sellers, they keep a landline. I suspect that is because many years ago I needed to fax something and we had long since given up our landline. This datapoint always works its way into the discussion of getting rid of their landline.
Don't get me wrong. Reinforced many times in my life is that you can lead a horse to water, even push its head into the trough, but you can't make it drink.