The problem is that it's very hard to get a consistent result - multiple injections sites are required and it's a gamble how it will stick. And it can randomly calcify years later.
Plasko,
Re: ". . consistent result". Yes. You are right. It is hard to do well. It appears to be deceptively simple and straight forward. But it is really more involved than it appears.
That is where the training, experience and artistic ability come into outcomes. I hear reports of recent horribly "over done" fat grafting outcomes.
However, it also remains true that a few of the best plastic surgeons do get remarkably good and consistent results.
But you are right, other surgeons do also get inconsistent and mediocre results.
Checking the reports on the internet - - calcifications appears to be pretty rare and more often associated with the donor site in liposuction - - rather than simple fat harvesting for transfer. However, it is reported.