The main reason is technology and materials, because if you make one, you don't need any technology, and it is acceptable to have some deviation when cutting. But if you do two, the requirements are relatively higher.

Personally, I don't recommend doing this operation. The first person likes big ones and doesn't like fake ones very much.

Second, this kind of operation is risky: although the success rate is high, it will leave sequelae, sometimes pain and lumps, and it is not conducive to breastfeeding in the future. Other risks have no scientific basis, so you can search online.

In a word, you must think it over before doing this operation.