The FBI's internal guide for getting data from AT&T, T-Mobile, Verizon
Indeed, often people have said the FBI runs this and that.
But this is not cost efficient, the agencies can just subpoena the businesses for data, simple as that.
No hacking, no developing etc.It's pretty efficient, if the government announced they would save some files on all citizens, it would be widely unpopular.
So let the people use the services they consent to use, let the businesses collect as much data as possible, the more, the merrier.And when the need for these resources arises, subpoena the business, they'll even do the search for them.