Most people don't have the scientific literacy to distinguish good science from bad with any amount of research, and know this. Even if you had some reason to think that this probably-a-scam thing had enough of a chance to be worth expending nontrivial effort to check out, it's hard to distinguish a good scam from a weird truth.

Once someone's decided (unconsciously, most likely) that they want to avoid cryonics because it seems sketchy, they will generate excuses to avoid it without having to actually say outright that they think it's a scam, because accusing people without hard (scientific, not Bayesian) evidence of guilt is socially inappropriate.

I'm not sure about the high status people with relevant background information, though I do note that that demographic seems more likely per capita to actually sign up. However, I would speculate that academics may be leery of being seen to take seriously anything "fringy" that might damage their reputation, and will endorse any line of argument that appears to oppose it.