Just found out that you can stop this.
By default, Google, and possibly others, use your SSID to help improve their location services. You can opt out by changing your SSID, shouldn’t it be if you want to opt in? Anyway if you add “_nomap” then they won’t record your data, alternatively maybe hiding the SSID does the same?
More details here: https://support.google.com/nexus/answer/1725632?hl=en&rd=1