"At what age do you think a granny should acquire a smart phone? I haven't got one yet." Neither have I Varian. Though when I was in hospital recently husband lent me his, and I managed to call home a few times.
I agree it's too late to put the genie back in the lamp now, but the aspect that worries me is that it cuts down the time children have for exercise, face to face socialising and forming relationships, to some extent original thinking, etc.
As for when our grandchildren started, one family is almost banned altogether, another is rationed, and the eldest is an adult now, I don't think she had one as a young child.