This has also been a common theme in recent decades with respect to privacy.

In the US, the police do not generally need a warrant to tail you as you go around town, but it is phenomenally expensive and difficult to do so. Cellphone location records, despite largely providing the same information, do require warrants because it provides extremely cheap, scalable tracking of anyone. In other words, we allow the government to acquire certain information through difficult means in hopes that it forces them to be very selective about how they use it. When the costs changed, what was allowed also had to change.

I think of this in reverse. It's legal for the government to track mail - who sent a message, and who it's going to. They have access to the "outside of the envelope". But it's not legal for them to read the message inside.

And this same principle allows them to build massive friend/connection networks of everyone electronically. The government knows every single person you've communicated with and how often you communicate with them.

It was never designed for this originally.