If I may take a stab at this: it’s probably a combination of
1) Costs a lot
2) Benefit isn’t expected for many decades
3) No guarantee that it would work
Anyone taking a heurisitc approach to reasoning about whether to sign up for cryonics rather than a probabilistic one ( which isn’t irrational if you have no way to estimate the probabilities involved available to you ) could therefore easily evaluate it as not worth doing.
If I may take a stab at this: it’s probably a combination of 1) Costs a lot 2) Benefit isn’t expected for many decades 3) No guarantee that it would work
Anyone taking a heurisitc approach to reasoning about whether to sign up for cryonics rather than a probabilistic one ( which isn’t irrational if you have no way to estimate the probabilities involved available to you ) could therefore easily evaluate it as not worth doing.
The religious might also see it as an attempt to cheat God, which rarely ends well in the mythology.