Is there an under-supply of blood in rich countries to the point where people are dying as a result? If 1 regular donor stopped donating, how many additional people will die?
There's lack of supply of some rare blood types[1]. Also relevant to point out, if you go donating blood don't just go after some disaster hits. It's a common occurrence that tons of people show up for blood donations after some tragedy hits but blood can only be stored a limited amount of time and it tends to be wasted. If you want to donate, go regularly.
[1]https://www.blood.co.uk/news-and-campaigns/the-donor-magazin...