Why does ONLY some connections have 'addrlocal' in getpeerinfo output
I would guess addrlocal shows you your endpoint of the connection, that is your IP address and port number. For all incoming connections that would be the same as the IP address and port you are listening on, so that's why it's not displayed. In your case most likely: 137.122.81.217:8333

I'm not sure what would happen if the server is multihomed.