Hospitals need blood for many other ailments, and folks are reluctant to give blood right now for many reasons (some legit, some not).
Blood has a short shelf-life.
https://www.oneblood.org/about-donating/blood-donor-basics/what-is-blood/why-blood-is-needed.stml
Hospitals will still continue to get their usual number of people who have been in car crashes, muggings, etc, who will need emergency surgery and thus blood.