First of all their metabolism's run faster than mine. They are alot younger than I am. Probably the picture was airbrushed digitally to enhance and beautify these young men. They are at a swim meet in some sort of either High School or College setting so naturally they would be standing around in speedo's. Board Shorts are for surfing and general swimming. These young men are proffessional swimming athletes.
Ultimately, who wouldn't envy a body like that. Vanity is vanity but looking good like that, is supposed to be envied and they probably don't think that what they are older men, all that good looks is going to somehow, go "poof". Hell I would even wager that one of these young men in this photograph might not live past their 40th birthday, due to STD's, Alcoholism, Drugs, or just accident of some sort.