Maybe procrastinators are trying to over-estimate it to get themselves to do it...

The probabilities are nuts though. For the whole thing to be of use,

1: you must die in a right way to get frozen soon enough and well enough. (Rather unlikely for a young person, by the way).

2: cryonics must preserve enough data.

3: no event that causes you to lose cooling

4: the revival technology must arise and become cheap enough (before you are unfrozen)

5: someone should dispose of the frozen head by revival rather than by garbage disposal or something even nastier (someone uses frozen heads as expired-copyright data).

Note that it's the whole combined probability that matters for the decision to sign up. edit: and not just that, but compared to the alternatives - i.e. you can improve your chances by trying harder not to die, and you can use money/time for that instead of cryonics.

edit2: also, just 3 independent-ish components (freezing works, company doesn't bust, revival available) with high ignorance get you down to 12.5%