Using wrap or something constrictive to flatten down breasts to make them less noticeable.
Constantly having something like that tightly wrapped around your body while going through puberty will cause it to grow in a fucked up way since your body can't fill out naturally. Some women do the same sort of thing with corsets to give themselves freakish hourglass figures by forcing their midsection to narrow.
Obligatory corset ree but
It's the
misuse of corsetry that will cause the body to deform, as in tying it waaay too tight and wearing it too long (i.e. for days at a time). If you use it properly, a corset works like spanx and is actually pretty comfortable. The fashion craze that led women to abuse corsets caused literal deaths because it wasn't how they were meant to be worn
, not because everyone just thought it would be cool to have deadly, painful underwear. Why would they stick around for centuries otherwise?
For a modern equivalent, imagine if it suddenly became cool to wear 3 pairs of heels strapped one on top of each other, and in 100 years people will be saying that it was fashion for women to break their ankles because of the idiots misusing their shoes to look "cool".
With binding, on the other hand, there's no way to use it "properly". Even with the pithy guidelines companies give out, like "take breaks" or "don't wear it in the heat", its construction makes shallow breathing and deformation an inevitability. There's no way to adjust a binder, for example. And I really don't trust children to measure themselves accutrately, so it's probably too small already.
Moreover, information on the harm binding can cause is extremely few and far between. If you really scour tumblr, maybe you'll find one "oh you might get a cough and have to go to the hospital!" But you have to put a gun to people's faces to get them to admit that deformation is a thing at all. Or breaking your ribs. Or collapsing a lung. Or breaking a rib in such a way that it stabs into your lung. Or give yourself permanent breast sag.