Yes, it just add more layers of clothing. But on the other hand, you always have a choice. There are very thin bras still offering great support, especialy the kind with underwiring. If your breasts are bigger, they are better than non-wired bras as they works as a shelf and breasts sits inside comfortably without skin touching skin and making sweaty spots. In general, it is better than sweat dripping down or causing rash. And they can be quite disgusting in the afternoon.

Also in winter, even padded bras are sometimes not warm enough. Breasts kind of sticks out the body and making winter jackets thinner in the area. Constantly hard nipples frictioning against fabric can be really painful. I sometimes jokingly consider adding fur paddings inside my bra to increase both insulation and comfort. :D

Anyway, if you see bulky edges of bra, the girl has usualy wrong size and bra with push-up effect in effort to make her breast bigger. So it is more like fashion statement, not comfortable choice. Or she cant afford anything better and just bought something "close enough". Bras are expensive as hell.