According to US government-speak, the answer is “because they’re addicted.”   

Fortunately, more rational minds know differently. Most recently, a Canadian research team took the time to actually interview various cannabis consumers. Their findings appear in the current issue of the journal Substance Use and Misuse, and provide a telling, albeit predictable, look into the motivations of the ‘typical’ marijuana user.

Why do tens of millions of adults all over the world smoke pot?

In short, because they enjoy it!

Understanding the Motivations for Recreational Marijuana Use Among Adult Canadians

Substance Use & Misuse, Vol. 43, Issue 3 & 4, February 2008: pages 539-572

The primary purpose of this study was to develop a better understanding of what motivates a selected group of adult[s] to use marijuana and to explore the social contexts in which it is used. …. Using interviews to gain insight into the subjective experiences of the participants, this research corroborated the results of previous studies that found that most adult marijuana users regulate use to their recreational time and do not use compulsively. Rather, their use is purposively intended to enhance their leisure activities and manage the challenges and demands of living in contemporary modern society. Generally, participants reported using marijuana because it enhanced relaxation and concentration, making a broad range of leisure activities more enjoyable and pleasurable.