What’s the deal with “Private name, private number”?

Caller ID may have been developed so that we could avoid annoying telemarketers, but now they are the only ones who mask their numbers – aside from the people who work at Los Angeles’ City Hall. Caller ID is so ubiquitous that it has become a red flag when the display reads “Unknown caller” or “Private number”, so why does the Mayor’s office have blocked numbers? Anyone? Jon Goodman, President