And for me, every time I smoke pot I become absolutely useless. Anything more difficult than watching whatever the hell happens to be on TV is nigh on impossible for me. And I don't normally watch TV! Anecdotes are fun.
Nobody talks about dosage when they talk about cannabis, why is that?
For example, downing a bottle of Jack vs. having a couple of beers. Unless a severe alcoholic, no person will be good for anything after the former (health risks not even included), whereas you are not really impaired after the latter.
Dosage matters, and that's true for cannabis as well. Most people won't be very productive/active after hitting the bong or whatever, lightly vaporizing some sativa strain, different story.