We can start freezing people now. The question would be, since cryo worked, why we didn't start freezing people when we already knew it could work in principle and had the technology.

We haven't proven it cannot work. But we don't know if we're doing it right. We don't know if just the head is enough, or if including the whole body slows the process so much the brain is damaged. We don't know if we're using chemicals that best accommodate thawing or scanning, whichever turns out to work better. We don't know if waiting until death causes some kind of irreversible damage or psychological problems.

It isn't that simple. You can't just toss people in a freezer and figure out how to revive them in a few centuries. We already know that the freezing process damages and destroys tissues.

I'd argue burying them or cremating damages and destroys tissues even worse.

We obviously don't care that much, not for the price of ressources needed.