I had roughly the same injury, shattered tibia, eight screws and a plate. I am allergic to opioids, they make me itchy, twitchy, and uncomfortable. I could only handle very low doses of codeine and extra strength ibuprofen. I normally don't partake in MJ because I don't like the buzz. However, during the first couple weeks, a couple hits of MJ was the only thing that helped me to sleep.

Both of these stories are anecdotal. There are vastly varying levels of addiction tolerance among humans. Just because you had a good experience without addiction does not mean that others react the same way. 

Opioid addiction is often about chronic pain, which probably should have been managed with other methods, that requires larger and larger doses to manage as tolerance grows. 

There are also many factors that lead to people "seeking to get blasted out of their minds" mental illness like chronic depression and PTSD to name a few. Judging others based on your experience is myopic.