I beg to differ, textiles tend to accumulate bad odours because the liquid gets impregnated, Meanwhile if you are shirtless sweat is going to fall to the floor and your skin will not absorb it and accumulate sweat odour. Still, if you smell bad without a shirt you are going to smell bad with one. You motherfuckers need to have a proper hygiene.
This only applies if you sweat into a shirt for a longer time. Concert only takes ans couple of hours and the shirt is clean beforehand. As long as it is not soaked it serves as a barrier for bodily odors.