Why Are There Drawstrings on the Bottom of My Shorts? [Video]

I'll admit I'm not the most fashionable guy. I talk on the radio so I don't have to dress up for work. I'm about comfort first, and if I look decent second. And I'm practical too. Things need to have a purpose, a function. That's why I'm so confused about drawstrings around the bottom of my shorts.

Can someone please explain to me what I'm supposed to do with these? Seriously, I really want to know...although by the time you read this I will have already cut the drawstrings out.