Why do they put men with big packages on underwear packages like boys want to see that?

My friend Matthew never wears a belt to school and his pants get a bit lowered. He wears Calvin Klein boxer briefs like me. One day in the bathroom I said Matthew your pants are falling down I can see ur underwear and he said its ok its Calvin Klein, everyone has calvin klein. Then I said maybe tomorrow u should bring a belt so his pants don't fall down and he said I don't care if my pants fall down. So the next day when we were changing for sports I said so you don't care if your pants are falling down, ok. Then I went up to him and pulled his shorts down. I saw his Calvin klein underwear. We were @ a sleep over and we underwear sweared on not telling the girls we liked. Underwear swear is when you take off your pants and switch underwear in front of each other to ensure trust between us. It was really fun.