no kidding chaz, it must be a joke. 4-15 strokes. i assume thats one complete in and out motion. if people are only doing that 15 times, ill tell you what the likly causes are.
they are sex/pleasure addits just looking to 'get off', get there "fix".
they are 12 years old and have suck deep lust they prolly dont even get to love the women they go before "it" takes place.
its a one night stand, again this would fall in the catigory of sexual perverion.