The concern is that if the site is insecure you might send Geolocation which might be sensible information through unsecure channels allowing someone to snoop o

The concern is that if the site is insecure you might send Geolocation which might be sensible information through unsecure channels allowing someone to snoop on the connection and read that data. In other words they are trying to hide the geolocation data from proxies, Carriers, ISPs and someone possibly MitM attacks