Just like many addictions, just because you know the negative side-effects doesn't mean you are willing to give up the activity. Plenty of people know how bad fast food or smoking can be, but the trade off of feeling good while doing it is too good to pass up.

A lot of times I find myself picking up the phone to message one person, but I end up on a 15 minute journey scrolling through whatever social media I am on and almost forget my initial intention. Disciple is obviously a big factor here.

I think this can be managed without totally getting rid of your smartphone. Like the saying goes: "out of sight, out of mind". Everyone's mileage will vary though, just my 2c