Until this study was done, we did not know if these objects could have affected humans. Imagine if they _had_ discovered the ability of PBHs to e.g. puncture a lung, blood vessel, or brain synapse. Maybe we would better understand e.g. crib death, or Alzheimer's disease.

Wouldn't any parent line their baby's crib with the mass equivalent of a million aircraft carriers in lead, to protect them?

We have a hard time understanding what dark matter is. There are theories that some of the dark matter could be tiny black holes left over from the big bang, called primordial black holes (PHBs).

How can we detect PHBs if they exist? If they existed in large numbers, would we notice them? The paper says that you would notice a PHB if it went through you, since you would likely die. We are not noticing people dying by mysterious gunshot-like wounds without guns in any large amounts, so there can not be that many PHBs around.

The paper is (weak) evidence against a large amount of PHBs. The paper is also slightly funny.