It is very easy to do. In most cases masturbation is self-taught.
It is free. If you are horny and your cock (or pussy) is twitching just pull down your pants and work it out. No financial cost is required.
It is safe. Unlike other addictions like alcohol, tobacco, drugs or even unprotected sex, masturbation is perfectly safe.
It causes no health hazards. Smoking causes lung cancer, alcohol causes cirrhosis, drugs may even cause death. The only health risk associated with masturbation is if you do it too much. But then again exercising too much is unhealthy as well, and exercise is perfectly healthy.
It does not cause obesity. All that stroking motion probably burns some fat.
It does not smell bad. Everyone enjoys the smell of sex
IT IS NOT IMMORAL!! The people who say that they are immoral often use lame excuses, and mythologies that have no scientific basis whatsoever.
It Is a lot more fun. No drug on the planet can beat the climactic feeling of orgasm. Let's face it, for those of you who are drinkers or smokers, tell me if you honestly enjoy that more than masturbating.
It is the best form of satisfaction. When you masturbate to orgasm, you feel great, you rest for a while a few hours later you are horny again. You can do no harm to your body (blisters aside). For a drinker for example will drink a dozen cans of beer, he'll feel happy and ecstatic for a while that is until you find him puking in the toilet.
It allows you to live out your fantasy. All human beings have dark, sexy fantasies. Most of them, however, are extremely dangerous or immoral. But you could masturbate to it.
It is an amazing psychological and physiological high without the use of drugs, alcohol or anything of the sort.
It's side effects are minimal and not very dangerous.
It is perfectly natural and refreshing
It can be done selfishly, without worrying about the feelings of another person.
When they say the best things in life are free I think thats what they mean.