Something I've noticed: in the US people generally have an aversion to being even mildly uncomfortable.
And, it's culturally acceptable to be on medication so people take it for basically any inconvenience.
Sweating a little? Crank the AC. Small headache? take a pill. Bad day? Have a drink. Workout left muscles sore? Another pill. Sprained ankle? Obviously you need pain medication!
It's easy to see how there is a low threshold to abusing pain medication.