> Why can't the fourth amendment follow contracts? Why can't I trust my location data to AT&T and no one else?
The 4th amendment protects people and places, not information. You have a right to privacy in your person and your house, but not on information you entrust to AT&T because you have no expectation of privacy on AT&T's premises.
> Third parties are necessary for most communication.
The 4th amendment only indirectly protects communications. It was mainly designed to keep police from breaking down your door to search for items you hadn't paid import duties on. The idea that it protects bits flowing through other peoples' wires is itself a bit of a stretch. The first time wire-tapping came up in front of the Supreme Court (in the 1920's), it was found to not require a warrant under the 4th amendment. After all, it wasn't your apartment being tapped, but some location in the telephone company's office.
Why does the Fourth Amendment specifically and additionally call out "papers and effects" when in your view "persons and houses" is all it actually protects?
The 4th amendment protects people and places, not information. You have a right to privacy in your person and your house, but not on information you entrust to AT&T because you have no expectation of privacy on AT&T's premises.
> Third parties are necessary for most communication.
The 4th amendment only indirectly protects communications. It was mainly designed to keep police from breaking down your door to search for items you hadn't paid import duties on. The idea that it protects bits flowing through other peoples' wires is itself a bit of a stretch. The first time wire-tapping came up in front of the Supreme Court (in the 1920's), it was found to not require a warrant under the 4th amendment. After all, it wasn't your apartment being tapped, but some location in the telephone company's office.