I think it’s the “if they are going to lay flat against your torso” bit that is a false premise, as far as many of us small-to-medium-breasted types are concerned. Regardless of whether I’m wearing a bra or not, there isn’t any flesh touching flesh, and therefore nowhere for sweat to pool.
I’m sure this is different for many women who are larger-breasted or just differently shaped, but that pretty much illustrates the point I’m trying to make – not all women are designed the same way, and therefore they’re not all going to be comfortable in the same garments.
And I’ve already said that this is only true if if you have boobs of any real size. When you have C or larger cups, flesh is gonna touch flesh, even if they’re perky for their size. And in this weather, sweat will happen and it’s just very uncomfortable. I tend to wear sports bras when it’s hot out b/c they absorb the sweat better.
Believe me, I envy you if you don’t have to worry about this, not only the physical comfort, but the not having to spend lots of $$$ on bras.