Pros:
--Telephone wire tapping laws protect you against unlawful surveillance by law enforcement ( They'll do it anyways but won't be able to bring it into court. Unless they had a warrant for collection)
-- Local to local calling ( no Russian hackers or DDOS from around the world) tell the telephone company to block international calls.
-- Domestic to Domestic Communications ( No lawful interception or bulk collection by your country's intelligence agency (NSA etc) They'll try to anyways I'm sure)
-- can access from any telephone jack in the city with a local area code (identity anonymous)
-- can access long distance out of area code if allowed.

Cons:
-- Likely to be recorded by FBI and local law enforcement, your telephone number is known (BBS server) and same for the BBS client callers, numbers and duration will be recorded at minimum. (Not location anonymous).
-- There are not really any of these out there (like < 20. I called one up long distance recently to test it out)
-- Un-encrypted communications. Not private or secure.
-- BBS operator takes on all of the risk, for content posting, and has to pay for an extra line.
-- Slow data transmission rates, can't share large files etc.