I gave blood routinely for years and years. Hours of my time on public transit and in the chair. Then, one time, I was sick and canceled because that is expected (nobody wants sick blood). They called me twice daily while I was sick to reschedule. Each time I said I would reschedule when I was healthy, but they didn’t stop calling. It made me think of them as some telemarketing predators that are profiteering on my good will. True or not that feeling made me not go back.
So that they can continue to function. Or are you planning on donating to pay the phlebotomists.