Why Are Jaw Implants Such an Uncommon Procedure?

After getting a chin implant one month ago, which I really like, I'm now considering getting jaw angles implants. Here in Europe, it is really uncommon to find a surgeon who's familiar with this procedure and there in the US, it looks like there are only a few surgeons nationwide who do them, and still it is not as frequent as chin implants.I think if well done, jaw implants bring dramatic changes to one's face - maybe more than what chin implants do. Are they uncommon because they're somehow more problematic? Is flying to the US a good idea (possible post complications)? Thanks.