Homosexual men are still banned from giving blood in many countries. In Sweden this changed less than 10 years ago. In Germany that changed in 2017, and in Austria they are still not allowed to give blood.
Same in Denmark, they're still not allowed. I donate as often as possible, for my homosexual friends who want to, but can't.
Or forever, depending on the country.
Regular Blood donor in the UK but cannot give blood in NZ because of mad cow disease.. Even though I've been vegetarian for over 35 years!
What it amounts to is that there isn't really a shortage of donors (there are brief local shortages). So they are optimizing away really small risks.