> Given the high correlation between COVID# cases (or %Positive) and hospitalizations, why not just use COVID# and "gain" 2 weeks of information?
Because it is not given and - if given - is not reassuringly close to 1. Correlation is positive, alright. But if you calculate hospitalization as percentage of cases, even adjusting for a lag, it is far from constant. Eg in Canada this ratio was 6x time higher in the first wave than in the second. It strongly depends on testing policies and hospital admission criteria.
Sure, over the whole run of the pandemic the case count has to be adjusted for changes in the testing regime. But in many countries the testing has been reasonably constant for many months, so the case count is a good indicator of the state of things.
The most vulnerable people are being vaccinated right now, so we should expect (hope?) that the number of hospitalizations and deaths will decrease significantly even if the number of cases does not.
Because it is not given and - if given - is not reassuringly close to 1. Correlation is positive, alright. But if you calculate hospitalization as percentage of cases, even adjusting for a lag, it is far from constant. Eg in Canada this ratio was 6x time higher in the first wave than in the second. It strongly depends on testing policies and hospital admission criteria.