The incentives are very different. When the doctor says injections or implants will set you back $X it's not a matter of life and death. Or even health at all. You can choose to wait and save up. When the doctor says you need medical treatment that costs $X you're going to have to come up with a way to get the money even if you go broke trying. And that's assuming you're lucky/healthy enough to even be given a chance to price shop.

It's hard to go broke getting boob jobs. It's exceedingly easy (in US) to go broke getting even the most basic of health care.