Because that's not legal, so they sell it to third party data brokers and it gets resold to someone the TLAs can buy it legally from.
Illegal to share data with entities that are themselves law enforcement, and which they are known to be demanding, not just asking to share out of good will?
US wiretapping operations are not bound by publicly-visible laws.
https://en.wikipedia.org/wiki/United_States_Foreign_Intellig...
https://en.wikipedia.org/wiki/Foreign_Intelligence_Surveilla...
https://en.wikipedia.org/wiki/NSA_warrantless_surveillance_(...
https://en.wikipedia.org/wiki/Room_641A