Just adding my two cents here, but this might be an example of survivorship bias - if enough of the weak, elderly, frail, already sick etc. people died before they could be taken to a hospital (or their relatives couldn't afford treatment and didn't even attempt to call a doctor) then the hospitals would have been full of people "in their prime" instead, skewing the statistics accordingly. It would not necessarily be that "the young were remembered better" but instead that only/mostly the young and healthy patients made it to the doctors in the first place.

Not surprising. This was the time before antibiotics, medical treatments were often lacking in any sort of evidence, and there were no widespread vaccines. Chronic conditions in the young were far more common than today - think latent tuberculosis, after effects of polio, rheumatic heart disease, parasites, chronic environmental lung diseases (silicosis, coal miners lung, etc.). Even basic nutrition wasn't sufficient in many areas of society.