Part of this rests on the claim that we, the freeborn citizens of the “land of the (used to be) free”, don’t “enjoy a reasonable expectation of privacy” when we use our cell phones.
In U.S. v. Miller, 425 U.S. 435 (1976), the Supreme Court ruled that we don’t have privacy in banking because he knows that the teller could see his account when he came in to make a deposit. (!!??)
So, this is just one more dot in the long line of dots that, when connected, allow government to erode and corrode the Fourth Amendment when it comes to the unalienable right to privacy in our persons and papers.
Well, that's not exactly what the court held. The court said, correctly, that negotiable instruments are inherently not confidential, hence the "negotiable" part.
You can't write a check to someone and then claim that check is privileged or confidential. That check is a negotiable instrument that could theoretically be endorsed and transferred to any number of people. The signor of the check knows this - or at least they should - when they sign the check, effectively waiving any expectation they might have enjoyed.
"...effectively waiving any expectation of privacy they might have enjoyed."