This one is obvious, but for those who don't, here's a compelling reason: you have an errand pop-up, post-workout, but you're wearing a hot dog eating contest shirt from the 1990s, complete with a 30-year-old mustard stain. Or it's 20 degrees outside, but you're wearing a sweat-soaked t-shirt that's sticking to your back and it feels like 10 degrees.
At least pack a spare shirt, even if you’re showering at home.