I smoke because i like to get high. I am guessing you have never smoked, judging by your biased comments. The problem with TV is that for a person that has never smoked, their minds get filled with nonsense from those bullshit commercials. Kids getting ran over by stoners in the drive-thru, kids falling in swimming pools because their babysitter was smoking, people stealing their parents money to buy weed, etc. All of those commercials are absolute fucking bullshit and nobody should believe any different.
And as far as the smoking question, especially the part about smoking occasionally, It will do very little, if anything to your cardio. The fastest guy on our track team and a lot of members of our state championship wrestling team smoked weed, some of them smoked all the time. Taking 6-8 hits of weed every week or two, while it won't benefit you, will also not hurt your training too much, if at all. Smoking everyday, especially blunts, well, I can't really argue with that, because over time it will hurt your training (but still not nearly as bad as you think).
You are probably one of those people that eats doritos and fast food all the time, but criticizes others for their habit. if you train hard, and have the talent and killer instinct it takes to be a fighter, smoking will not matter, but if you are a pussy that trains and has no real talent or aggression, you could never touch alcohol or weed for your entire life and get your ass whooped senseless by a pothead.
Bottom line, don't criticize other people and their choices just because you haven't tried it, because you know absolutely nothing about it, and just have you're biased opinion. If you don't smoke and never plan to, good for you, but it doesn't make you a better fighter/person/athlete/student/anything than somebody who smokes all the time. For example, Carmello Anthony, Ricky Williams, Sakuraba, and many other professional athletes smoke, but when it comes down to what actually matters, on field/in ring performance, they step it up.