Solar facts laid out on a black long sleeve graphic tee. In a nutshell, we've only got a few more billion years left of sun! That sucks!
Humans wear T-shirts for a variety of reasons. First, they might need to cover the top half of their otherwise naked torso in situations were doing otherwise is prohibited. Second, even in situations where it is acceptable to have a naked torso, humans may wish to wear a T-shirt for warmth, albeit minimal. Third, humans may need to wear a t-shirt so that their affiliation with a particular team, tribe, sect, or fascist group can be quickly and easily identified, and/or documented. And there are probably a great many other reasons for wearing T-shirts that simply aren’t occurring to me right now. Personally speaking, I wear T-shirts for the same reason I wear everything else, which is to use my body as a human billboard. If a particular item of clothing (OR accessories) is NOT liberally emblazoned with a sociogeopolitical message or slogan, I simply won’t wear it. Happily, this lovely longsleeve Altru t-shirt IS nicely emblazoned, so I bought it and I wear it. I love it.