This is how... adults dress.
Well, not tucking shirts into jeans. That's how old dudes dress. But typically when you're at work and you're not, say, ringing up a cash register or offering HJs for cash, you have to have your shirt tucked in. I wouldn't expect a nation of prison descendants to understand the formality of all. There's very few careers I can think of where you won't have a tucked in shirt on probably 90% of the time -- especially if it's a dress shirt.