There are maybe two or three people in the entire world who spend only the bare possible minimum on themselves, and contribute everything else to a rationally effective charity. They have an excuse for not signing up. No one else does.

If you are opening the scope to the entire world it would seem fair to extend the excuse to all those who don't even have the bare possible minimum for themselves and also don't live within 100 km of anyone who understands cryonics.