It's pretty baffling. When you suggest that people try simply not using Facebook or WhatsApp they act as though you just suggested they stop eating and breathing.

It's because most of those suggestions try to imply that people can't quit Facebook, because they're stupid or addicted or something. One should stop and consider here that just because you can, doesn't mean you should. A lot of people, myself included, get actual value from using Facebook and thus don't have a reason to stop using it, even though they are perfectly able to.

Your error is confusing "I can" with "people can".

No, I committed no error. You seem to be confusing what people strongly desire with what is actually possible.