You Mac does not know what network you want to join. Maybe you are over at your neighbors helping them, and want to join their network to give that help, or you are traveling and want to connect to the hotel network, or a coffee shop network.
The Mac cannot know when you are interested in the network you previously connected to or if you want to switch networks.
Hiding your SSID network name, just keeps honest people honest. It can be figured out with the correct software.
As long as you are using WPA2 (or WPA) WiFi security and you have a moderately good password, then all anyone will see is the name of your network.
The security is none, WEP (so old, the movie "Gone in 60 Seconds" is slow compared to how fast WEP can be cracked), WPA and WPA2. The client needs to know what security to use when connecting to a WiFi access point, hence the fact that it is advertised.
The BSSID is the nn:nn:nn:nn:nn:nn MAC address and that is visible anytime you transmit something, as that is the unit-to-unit addressing information, and is not encrypted. If you wanted to connect to that WiFi base station, you would need that BSSID to address the base station, otherwise it would not know you are talking to it. And when you do talk to the WiFi base station, "YOUR" BSSID is attached to your message so the WiFi base station knows where to send the reply.
The Country code tells what restrictions apply to the WiFi radios, power levels, and channels that can be used. It is important for the WiFi base station to tell that so that a client does not try to use another country's rules and violate FCC (if in the US) rules and regulations. So if you travel to another country, your Mac needs to know these rules when it talks to a WiFi base station while you are away. Same if you have a foreign guest you are allowing on your network.
The channel is the frequency the WiFi base station is transmitting on. Anytime a message a message is sent, it is trivial to figure out what frequency is being used, and thus the channel. Even if you hid your SSID, you are still sending out radio waves, that can be detected and the channel figured out.
Signal Strength/Noise, is again radio waves, and because your WiFi base station sending them, the receiver can see how strong the signal is and how much noise is in the signal.
If you are that concerned about these things, then stop using radios, and use wires between everything.
