I also found that a bit odd, it's almost like bra manufacturers in Europe think one of these is true:

* there are no smaller breasted women in Europe

* women with smaller breasts don't need to wear a bra

The 1st is plainly nonsense, the 2nd seems like it can't be true, although I can't really comment due to being the wrong gender.

Almost nobody needs a bra (as in their health won't suffer if they don't wear one; there are exceptions like large busted women whose skin rubs and will create sores). A lot of small-busted women either don't wear bras or just opt for tanks/camisoles. (Or just wear the wrong size because they don't need the support, they just need to show they're 'fitting in' and wearing what they 'should'.)

What lead me to think there might be some occasions where a bra is "needed" would be during sports, but as I said I'm entirely unequipped to make any kind of knowledgable comment in that regard and it's just that "sports bras" are a thing that gives me that impression.

For health reasons, they're not needed. For comfort/exercising viability, it's going to depend on the person and the exercise. Most smaller breasted women aren't going to need a proper sports bra. Exceptions are women who are nursing, trans women on HRT, and adolescents whose breasts are still growing. For those populations, it's normal for any kind of jiggling to be painful.

Most large breasted women do prefer/need a sports bra to prevent things like skin chafing and grossness that can result from prolonged skin to skin contact + sweat.

The numbers in that table are the numbers from the bra sizing system, not necessarily actual measurements. The EU system for some reason uses band size numbers about 10 less than the actual underbust size.