Easy. It's far too expensive to implement, both in money and man-hours. Especially man-hours.
The amount of people required to personally surveil the general populace is way too exorbitant, AND they have to monitor their own people to prevent leaks. The logistics explodes well before this becomes feasible.
Then there's discoverability. Once such hardware is out there, it's only a matter of time before it falls into the hands of someone capable of dissecting it. Given that such spying methods would be 'sold' to federal management on the grounds of national security, there's an interest in not having it fall into such hands. Therefore, these methods are reserved for high-profile targets. Not the average Joe citizen.
To summarize: Too expensive (money), too expensive (logistics), and too expensive (R&D). Unless you're on Interpol's most wanted list or something, you don't need to worry about this.