I think it's mostly just wishful thinking that makes them ignore the cryonics option and assume they will achieve functional immortality without being dead temporarily before.

I say that because I know it is true for myself. When I think about it rationally I estimate that cryonics is probably necessary. But when I think about it casually, wishful thinking overrides that. I guess that if I saw a poll on that topic and just responded immediately without thinking too much about it (because there are other things to do/other questions to answer), I would probably also say I don't think cryonics will be necessary.

I wonder how many people who replied to that poll made that mistake.