Actually, replacement nipples could be a huge step forward for women who are facing a mastectomy. Their choices are 1) mastectomy and reconstruction with no nipple, 2) mastectomy and reconstruction with a tattoo where the nipple was, or 3) a "nipple-sparing" mastectomy, which is a much more difficult procedure, carries risks because some tissue gets left behind, isn't always appropriate/possible for women with small breasts, and sometimes fails.
I was dating somebody a few years ago who was diagnosed with breast cancer, and went to most of her surgical consults. (She's fine now; thanks for asking...) Preserving the nipple was a big deal for her, even though there was a good chance that she'd never get sensation back. she went with the nipple sparing option, despite the potential downsides, and was happy with the outcome. (Her summary: "It doesn't look perfect, but it doesn't look deformed, either")
I suspect that if 3D printing of a new nipple was possible for her - and mitigated some of the risks, she might have gone with that.