drbill:
I've never understood a person's need to be mind altered on a daily basis, regardless of what their alterant of choice is.
I'd guess it's a combination of addiction/habit and state-specific learning. After a prolonged period of frequent use, NOT being under the influence of a given substance is what seems unusual to the individual, and is more difficult for them to deal with.
Despite the common perception of stoners as lazy, sloooooooow, and unmotivated, I personally know quite a few friends from "back in the day" that never gave it up. Despite this, they aren't vegetative couch potatos, but successful professionals who are active and productive members of their communities. While the sample size I draw from is unusually large by virtue of my knowing a large number of people, off the top of my head, I know of an attorney, a senior software programmer, a surgeon, a nurse, a fisherman, the head of a well-regarded non-profit organization, an accountant, a publisher, and a real-estate inspector who all are frequent, if not daily marijuana users. They seem to be able to function just fine, and aside from having what must be godawfully blackened lungs, bear little resemblance to what you might expect after having watched a Cheech and Chong movie. These are not "Dude, pass the munchies" folks.
I believe almost all of them to have the good sense not to get stoned before doing something that requires them to be on the ball, and in most cases, I wouldn't hesitate to trust their expertise while sober. That said, if any of them were divers (they are not), I wouldn't dive with them while they were under the influence. Even if someone is an experienced and functional recreational drug user on land, there isn't any assurance that the effects they are so accustomed to will be the same in a high pressure environment. If oxygen and nitrogen can become psychoactive 100' under water, I wouldn't want to take a chance on what the effect of pressure on already mind-altering molecules dissolved in my buddy's blood stream might be.
Freshwater tuna chasers I don't need.