It's not just your home network, it's also your phone. Not only does your access point or phone publish it's SSID it also publishes it's MAC address. In the case of your phone as a hot spot can be used by people to track your location using any of several web sites like WiGLE: Wireless Network Mapping. Then there is the other nastiness of wireless endpoints being vulnerable, and last but not least simply having an access point announces your presence to the world.