Fellatio is a sexual act involving the stimulation of a male's genitals using the mouth, lips, or tongue.

Kids do the kidly thing, and everyone over the age of 14 (18 for legal reasons ;D) goes for a costume house party and/or a night out involving a lot of drink :)

If you are going to drink Gatorade (or pop) Drink through a straw. If you drink from the bottle the pop goes directly over your 4 front teeth and those are the first to deteriorate and this is why you see many people with front teeth missing first. A straw helps it go directly to your throat over your tongue. Less pop on teeth.

involving how?

because they hear adults talk about their 'great night out involving alcohol' and want the same experience.

Also the sense of rebellion and feeling grown up