Do any of you guy readers wear tank-top undershirts? And, if so, can you explain what the hell that’s about?

So far as I’ve always understood them, undershirts are meant to keep you from sweating through into the outer shirt. But I – and I think I’m not the only one on this – mainly sweat from the armpits; that’s why we put deodorant there.

So, if a tank undershirt specifically doesn’t cover your armpits, than what, exactly, is the point?