Look, people aren't idiots - Bra sizes have CHANGED!!!!
The rule used to be: measure underneath your boobs and add 2" if an even number, 3" if an odd number. So if, like me you measured 32" under the boobs, you would add 2" to get 34". That would be your band size.
Then you measured your bust itself. If it was the same as your band size (in my case 34", you would be an AA cup. 1" bigger was an A cup, 2" a B cup, 3" a C cup, 4" a D cup. Therefore someone like myself with a 32" under band measurement and a 38" bust measurement would be a 34D. Which I wore for years with no problems at all.
Then a few years ago the measurement system changed to this:
Band size is what you measure under your boobs full stop.
Measure your bust itself. Cup size is AA - same as band size, A - 1" more than band size, B - 2" more than band size, C - 3" more than band size, D - 4" more than band size. , D - 5" more than band size, E - 6" more than band size.
So at 32" underneath and 38" "on top," under the old system I used to be a 34D but in the new had to move to a 32E.
My old 34D bras did not fit badly - they fit fine. It's only if I bought a 34D bra now that the system has changed that they wouldn't fit.
You can't blame women for continuing to buy the size bra they have worn for 35 years when no one has bothered to tell them the sizing system has changed.
I get so frustrated reading posts on here "Oooh it turns out I've been wearing the wrong size bra for 15 yeeeeears!!!" No, you have been wearing the right size bra for 11 years but all the new ones you have bought since the sizes changed a few years ago ARE the wrong size. It's not your fault!