So what they are saying is anyone already established in the circuit isn’t actually obliged to make any calls at all!
The original question was related to downwind reports, which are not required. If no one else calls, you don't have to say anything else in the circuit. If another aircraft calls, you are required to reply to provide situational awareness for that aircraft. Too many people forget the situational awareness part and only give the inbound and joining calls from habit and ignore everyone else. Listen before transmitting and then listen for any responses and learn the correct format for the broadcasts. Read the requirements again. Remember the last sentence. Use the radio more often if needed.