Tucked in Shirts

What's with people who tuck in T shirts to their sweatpants and shorts? What's with tucking in a T shirt period? Matter of fact, what's with tucking in anything unless you're wearing a longsleeve button up that you will later wrap a tie around the neck of?

As far as I know, tucking in is a formal thing, like a tux or a business suit. Its certainly not comfortable, and it definitely doesn't look good. I may not know, being at work right now, writing a blog, wearing a stained T shirt, ripped jeans, flip flops, and shaggy hair. The world of the water cooler corporate formal workplace is an alien concept to me. But I'm not talking about work, I'm talking about the gym and the super market and sunday on the promenade. Sweatpants and shorts have no place in the world of tucking in, nor does the T shirt.