As a pilot, it's valuable to be able to see tail numbers to help correlate what I'm hearing on the radio with what I'm seeing on my displays. I can guess who's who from position reports, but seeing the tail number leaves no ambiguity.

There are also some smaller facilities that use ADS-B to monitor traffic, but aren't networked into the national ATC radar system.

Aviation events will also setup their own temporary control tower, and frequently use ADS-B as an aid for sequencing traffic. (Again, without access to the national ATC radar network.)

For folks who need privacy, there are a couple options that already exist - UAT privacy mode or private Mode S addresses. Though notably, both of these are only available options for domestic flight within the US.