Carrie, I have seen that happen as well and a friend and I have been actively talking about the problem. Her observation is that many hit the wall right after transition (suicides spike at this point also) - when it comes home that life has been 100% trans this and trans that.
For these, this is the line that divides the quest for identity from living, from being trans from being a woman. If you don't know what you are, you have no business transitioning. This is what led to my comment about moving forward with life immediately on sorting out what you are and where you are headed.
Two things make people uncomfortable when it comes to the arguments of medical necessity, whether considered for SRS or FFS. The first are the philosophical arguments (which are rooted in puritanical and religious-based cultural bias, frankly). This is where arguments like "other people live with things like this, why can't the trans person" come from. There are also arguments of fairness, social utility, relative benefit, and more. It's a morass. The second is cost, coupled with the deep suspicion that someone is trying to pull something.
I'm not concerned with either one when it comes to FFS any more than I am with SRS. Both are incredibly invasive and extreme from a number of perspectives. Many start down the path, but few indeed complete it. Too many things conspire to disincent and stop those who don't really need them.
There may be some cause to be concerned for costs when it comes to facial surgery, but I think that could be resolved by appropriately limiting the procedures that fall into that category and assigning the costs of cosmetic procedures outside of that back to the patient, along with a pro rata portion of general surgery costs such as the hospital stay, mess, anesthesia, etc. That would eliminate those scamming their way under the flag of medical necessity to get something like a lip lift. Not too many people are going to undergo having, say, their forehead dissected and put back together just to cover a portion of the costs for the cosmetic plastics they are having done at the same time.