I’m sure there’s also a psychological reason. Dr. Birx has been very direct in talking directly to Millennials about how important it is that they abide by the rules. Getting them in to donate blood will pull them into the effort and make them part of the solution.
When I was teaching my students had the opportunity to donate blood and would do it regularly(some but not all will do anything to get out of class!) I’m thinking with the schools closed a blood supply line has been shut down and blood is getting in short supply.