Is this so?
I think of it like the time when Hong Kong was flooded with Opium.
"adults smoke opium"
If you find that too crass, there are countless other ways to put it:
"adults eat sugar"
"adults watch TV"
Just because everyone in the mainstream does something, DOES NOT mean that this is a good thing or a smart thing to do.
In fact, we can easily observe that the few adults who are at the absolute top of their game, the most skilled, the most wealthy, the most powerful... well guess what? They DO NOT use smartphones. They don't tweet. They don't have profiles anywhere.
Except for GPS directions, there is actually very very little actual need to use a smartphone. At work, you have a computer for access to Google. At home, you have a tablet or TV or books or a Kindle for media consumption.
You can just swipe a credit card for payments.
A smartphone is not at all needed to be a highly functioning adult.
In fact - it actually prevents you from ever unlocking your fullest potential by removing any chance for your brain to ever catch a breath and just be bored for half an hour and hear your own thoughts.