What makes you believe that? Cryonics is relatively well known among scientifically educated audiences. it's even the main plot device of a tv show aimed at general audiences (Futurama).

This physicist has never heard anyone talk about cryonics in meatspace, and assumed that the Futurama thing was fictional until reading Less Wrong. (Also, Fry was alive when he got frozen.)

Moreover, physicists are usually atheists, therefore in principle they should have no religous objection to cryonics.

For some not-very-large value of “usually”. Where I am, physicists aren't that less likely to be religious than random people the same age and geographic provenance (but it's probably different elsewhere).