Battlefield triage rules, essentially. Treat the folks who can be
treated most easily, so you can stretch overstressed resources to treat
the most people. And apply as sharply-defined a set of rules as
possible, to avoid getting into arguments over which bucket the patients
get tossed into. Same reason the Red Cross absolutely refuses to take
donations at aid sites no matter how convenient it would be -- in that
situation you can't afford even a hint of bribability or all cooperation
evaporates. A less-than-ideal decision process is better than a process
that people think can be gamed.
Having said that: It shouldn't be surprising that this sounds a lot like
the old civil defense brochures about how to deal with aftermath of a
nuclear attack. It's essentially the same problem, plus infectiousness.
Duck and cover... before you sneeze?