[SilasX]

The argument has the exact same form as the advice "don't talk to the police without a lawyer", and for the laws that support this protocol (right to silence/counsel). That is,

"I don't trust you to be an impartial seeker of the truth who's 'only' concerned with solving this murder rather than railroading me on random charges, therefore I will not answer even simple questions that you deem necessary to conduct your investigation."

(With that said, I really, really don't like the whole "don't talk to police" circlej---, like how it gets overapplied or dangerously applied ... but within a very narrow interpretation it's correct and well accepted enough to carry the implications over here.)

Edit: Correspondingly, the advice would carry a lot less weight in counties with a much better government that actually could be trusted not to look for petty reasons to arrest people. And so a government that prices itself a better steward of privacy could be trusted with key escrow.