The date by which surviving larvae in processed food will hatch. (Remember, the government regulations set thresholds below which insects and other contaminants are permitted in the food you eat in order to protect corporate profits.)
Processed food manufacturers presumably need know the hatch-date for their product, so they can set the "sell" by" or "use by" date at an earlier point in time. It may be viewed as better for business for you and your family to eat the food with bugs in it before they hatch so you don't know how contaminated it is.
Hatch-dates are not important for foods that are wet, pulverized, get embalmed in salt, or get sterilized by processing. You wouldn't recognize the contaminants, or at least they will not be crawling.
Hatch dates may be more critical for nuts and grains with a low degree of processing, such as oatmeal, chocolate covered nuts, etc.
All Grandma had to share with the kiddies were boxes of unopened fancy chocolate nuts, several years old. Each chocolate had a telltale pinhole showing where a newborn worm had escaped from its sweet lair, shortly after the hatch-date.