Because what doesn't kill you makes you stronger. There were some studies done a few decades ago in which they found genetic markers in people with names like "Levine, Levinson, Kohn, Coen, Levitts, etc. etc. etc. The priestly tribe of Levi was instructed to marry within the tribe which created a set of genetic markers that could be traced.
Anyways, one of the things they discovered was that this particular genetic marker allowed them to carry, but never get sick from a number of viruses, bacteria, pathogens, etc. Some of them did get sick when the Black Death came around, but they quickly recovered.
They also discovered, (although not with regards to this particular marker, but with regards to the Black Death in general) that there are also people who carry the AID's virus, but never become infected themselves. They're super spreaders yet they're immune from the virus itself.
If we look at people like Bill Gates, and other eugenicists, they love the idea of culling the population down to a few hundred thousand people. They want the world for themselves, and don't feel like dealing with all the problems of poverty, pollution, etc. except to just get rid of the poor and the gross polluters. Someone who has a healthy immune system that can handle viruses, pathogens might also be more than happy to cull the population of the planet by infecting the unwashed masses so that they can enjoy the rest of the world without having to keep bumping into so many sick people everywhere they go.