>>19558735It's because it's lifestyle induced.
Big tits don't automatically cause back pain - they grow slowly enough that the muscles in the back can grow at the same time to compensate. What happens is the girl gets bullied for standing out and starts to hunch over to hide them, this bad posture causes the back pain. Bras also can cause pain, especially if they fit badly, since they transfer some of the weight to the shoulders where it's not carried naturally. Good bras for large tits can cost 50-100 each so it's no joke, and bad fitting ones will fuck up your back.
So depending on when they developed, how fast, how they reacted to it, and whether they can afford/know about proper fitting bras combine to create the issues.
Generally you may notice that late bloomers tend to not have much pain and be proud of their tits (they are sexually mature and like the attention at that point), while early bloomers are shamed and hunched (they are not sexually mature yet and are bullied or afraid of the attention). It's all caused by the social aspects.
