The idea that regular cannabis use leads to sloth and apathy has been widely held for over half a century. In the 1930s, a federal bureaucrat trying to collect money for the Drug Enforcement Administration popularized this false stereotype. Nixon used the stigmatization of cannabis and heroin to target the Black community and distract protesters against the Vietnam War in the early 1970s—the issue of whether or not cannabis use causes a lack of drive stays open.
There is both support and refutation in the scientific literature for the theory that chronic cannabis use causes a lack of motivation and disinterest in pursuing one's goals. The medical society is still on the fence about this issue due to a lack of definitive evidence. It's hard to put a number on how much motivation someone has.
The American Psychological Association's (APA) scholarly journal Experimental and Clinical Psychopharmacology recently released groundbreaking research disproving the hypothesis that cannabidiol induces a motivational syndrome. "a pattern of cannabis use that is harmful and results in clinically significant impairment or distress," is how experts define cannabis use disorder. The report concluded that there was no proof to back up the hypothesis.