I'm looking at you GAP and Next in particular.
If it's warm I don't want to layer tops. I particularly don't want to layer vest tops. But at the same time I don't want to show everyone my bra.
If you can make t shirts and tops for men and children which aren't bloody see through why can't you do it for actual grown women?
Why is the choice sweat your tits off in twelve layers or show your tits off in one?