You are viewing it from one perspective and putting too much faith in that one data point. It reminds me of my daughter when she is doing something dangerous and I tell her "You are going to get hurt!"... "But I didn't!"
You are viewing pot, like a drug, as in cocaine-meth-style drug, rather than say, caffiene. A cup or three of coffee can be a godsend, but drinking pots throughout the day will kill you in more ways than one. Don't like that comparison? One vitamin is good. Six are not.