The organ donor thing is a good question. There are always problems with rejection so lifetime drugs are given to control this. Maybe it's not possible to make a transplanted gland functional, or, more likely, the insurance companies don't have it on their schedule for reimbursement. You would be surprised how many medical devices fail in the market place because the insurance companies won't reimburse. It is the true driving force, hidden behind the scenes.
More experienced companies work on the reimbursement issues first. I am sure that given the choice between your drinking more water and an expensive medical procedure (along with expensive anti-rejection drugs for life (and constant monitoring), they would choose not to reimburse. I am surprised that they will even reimburse for gland relocation.

What blows my mind is that basketball players make more then brain surgeons.