Some drug are legal and some not because legal drugs help your body (not including Alcohol and Tobacco. Illegal drugs affect your body in bad ways.
Simple answer: mammals have fur, reptiles and fish have scales, and birds have feathers. All three are simple variants of maturation in skin cells: if the cells just get thick, then you get scales....
Because some don't have the ability. That's true for individuals, As a species, all multi-celluar animals must mate or else become extinct.
Because there is a difference between eccentric and insane. It's often hard to distinguish between the two.
Fastpitch