legality
NSA has strict rules on what it can do with the information it gathers, so the gov can't legally use NSA mined data of US persons for anything other than FISA/counterintelligence needs.
The phone/tech companies can legally only track you, if you opt-in, eventhough all the data is already mined, unless requested per court order.
But I think they want a legal way to track you 24/7 without people opting in or per court order.
To further elaborate, let's look at the FB app as an example. By agreeing to the TOS, a user gives FB permission to record and track them, look at their contact list, etc. But all that information can only technically be used to improve service and experience.
But if contact tracing is allowed, then that opens up other possibilites for them.
Couldn't congress just repeal it with a veto proof vote?