"It does not matter how often people repeat this there is no evidence to support this broad claim. People are not replacing their PCs with smartphones (and neither tablets) what happens is that more smartphones and tablets are sold then PCs. That does not mean that people throw away their PCs and use them instead."

This doesn't change anything u still need GNU/Linux distribution(s) to recommend to your friends to use on tables/phones. It's the same story as it was and still is with PCs and Macs. What changed is devices list got longer and that is a good thing.