They actually weren't. One guy in particular I knew from band used to work very hard at trumpet, would always flaunt how good he was at it, and took school as a whole seriously. He then got into weed, and once we got to high school he stopped bothering to even show up half of the time, which in marching band is a big deal (especially when I was next to him in the form and had no one to dress to because he never -blam!-ing showed up, -blam!- you man, you made me look stupid), just barely got through his classes, went to summer school every year, just became a prick in general. TL;DR He worked hard and took life seriously, got into weed and became a lazy asshole. I get that there are some people out there who aren't like that, but weed made him a lazy asshole.