Spring singleton beans are supposed to be stateless though, so they can’t be called variables. Maybe the DI aspect of Spring is less relevant today in the micro service era, but in the day Spring helped make layered monolith apps much cleaner.

Yes, and notably, this isn’t about regular blood donation. Plasma donation specifically is a time consuming process, taking 1-2 hours. I don’t think not compensating regular blood donors results in the same kind of shortage.

The status quo is dependence on paid plasma, we import about 80% of our plasma from the US, because you don’t get enough donors when you don’t compensate them. Everyone else in the donation chain gets compensated (phlebotomists, doctors, nurses, receptionist…), and there’s nothing wrong with compensating the donor as well.