You are mistakenly inferring the wrong general principles from special cases that are well-known because they are exceptions to, rather than illustrations of, the generally-applicable rules.
The existence of these special cases demonstrates that a loss of the expectation privacy does not inherently occur when one entrusts another entity with some detail of their lives.
That expectation of privacy is created by the (well established at the time of the Constitution) common law lawyer/client privilege, it is not a generally applicable privilege that applies to commercial relationships and creates an expectation of privacy within those relationships. So, yes, there is an expectation of privacy here which has significance under the fourth amendment, but it is not one which extends to other business relationships like those between a telephone customer and their carrier.
The extent to which commercial relationships pervade our lives is, in my opinion, just cause to expand the boundaries of a reasonable expectation of privacy. The lack of transparency in how companies handle customer data, what data is retained, etc., especially for non-technical users, is further reason to codify clear rights to privacy instead of relying upon impenetrable common law precedent.
The existence of these special cases demonstrates that a loss of the expectation privacy does not inherently occur when one entrusts another entity with some detail of their lives.
That expectation of privacy is created by the (well established at the time of the Constitution) common law lawyer/client privilege, it is not a generally applicable privilege that applies to commercial relationships and creates an expectation of privacy within those relationships. So, yes, there is an expectation of privacy here which has significance under the fourth amendment, but it is not one which extends to other business relationships like those between a telephone customer and their carrier.
The extent to which commercial relationships pervade our lives is, in my opinion, just cause to expand the boundaries of a reasonable expectation of privacy. The lack of transparency in how companies handle customer data, what data is retained, etc., especially for non-technical users, is further reason to codify clear rights to privacy instead of relying upon impenetrable common law precedent.