Today's just-completed little shopping trip bike ride was a useful reminder of some reasons why in warm(er) weather I want to use one of my bike jerseys instead of my ordinary t-shirt. The bike jerseys don't necessarily keep me any less sweaty, but I can take them off afterward. And it's not even all that warm today.
(Bike jerseys also give me an easy way to carry my phone, which is useful for grocery stops. Today I just threw the phone in the panniers.)