If you think the governments of the world do not have the metadata of every single phone call and at the very least an outside picture of every letter being sent by non-companies, then I have a boat te sell you.

There is a legal process, though, at least in the USA.

You can get a warrant (a court order) to open a piece of mail, and the USPS isn't going to refuse to hand it over.

[technically they could, but someone would get stuck with contempt of court charges]

The post office and the phone company refuse to cooperate with law enforcement and offer disposable phone numbers and means to move money without trace/attribution?

The phone company has long cooperated with government. And while I’ve never heard of anything, the post office _is_ owned by the government in the US.