As for as I know, and I'd stress that bit, decisions are made by a transplant committee, that would take all sorts of factors into account, rather than just number on a list. But as few years back, we did see a liver transplant given to a certain ex-footballing hyper-star that was also famous as an unremitting alcoholic (and not totally isolated from drug abuse, if memory serves). And again, IIRC, the boozing didn't stop, with utterly predictable results. What we don't know (or I sure don't) is who else might have been a credible recipient.... if anyone.
I take the point about the child versus death-row inmate, and I doubt many people would argue prioritising the latter.
The problem is that such value judgments are easy at the extreme, they become increasingly problematic as the gap narrows from extremes, and gets very tricky between two equally acceptable and socially attractive candidates. We need a degree of constructive 'blindness' in the process, not just about race, sexual orientation, etc, but also social standing and wealth.
After all, the death row inmate might be falsely convicted and go on to be a world-class artist, musician or philosopher, and the little girl might grow up to be a mass murderer or a political dictator.