Here is another generalization; they also can be not all that motivated either (other than motivated to get high, but motivation as far as school, work, career — not so much).
Although the vast majority of people I knew in college those who smoked weed heavily were not in the scientific or technical programs or if they were, flunked out, there is a difference between association and causation.
Maybe those who were not that motivated "as far as school, work, career" would have had the same outcomes in their lives had pot not existed (association) as opposed to smoking pot causing such lack of motivation (causation).
Ps. If anyone cares to know genius smoked pot once during military service and then many years later (during my 40's) smoked pot a couple of times with someone I dated (who, btw, other than with sex, wasn't all that motivated). My only recreational drug is alcohol in the form of 12year old scotch although maybe at this point in my life "V" is now another recreational drug I use.