Sacred Haven of Debauchery

What's so silly about that?

I think a shirt is still clothing, um, how should I put it? Office attire, business attire, in general, with a slight touch of formality, a very slight touch, but still. And short sleeves just don't go with formality. A t-shirt with short sleeves, on the other hand, is perfectly normal, because a t-shirt is, by definition, very informal clothing.