If cereal were like pet food -- which is nutritionally complete and balanced with variants based on the particulars of the animal (eg. weight loss/gain, young/old formulations) -- it'd be unfortunate that parents had to resort feeding it to their kids but at least they'd be feeding their kids something healthy.

Somehow we understand nutrition so well that pets can live a long and healthy life eating exactly one type and brand of pet food but not well enough to make a determination on the healthiness of eggs that lasts longer than 10 years.