My wife and I will have to buy one soon, because it is pretty much the only way we can establish a line of communication with other parents of my young son's peers at kindergarten (he's nearing 3). Not doing so would stunt his growth on an emotional level, because we would deprive him of things like play dates and such. Not due to malice on the part of other parents, but because not having WhatsApp (here in the Netherlands) is not something other people can always grasp. We can choose who we interact with, but we can't choose my son's friends parents.
It's so incredibly silly how owning a smartphone isn't even a matter of preference any more; people just expect everyone to have one. I don't really need one, despite loving train travel and independent exploration on holidays. Paper maps work fine, preparation using a normal computer too.