How does the tracking network size affect functionality?
Apple and now Google trackers on the other hand build this functionality into the OS (or Google's near-OS bundle for Android), so if basically any phone comes within range of the tracker it will provide a location update.
Ability to actually find lost items. AirTags are so successful (in the US) because of the ubiquity of iPhones which are, effectively, constantly reporting on the location of detected devices. A smaller network of listening/reporting devices will not be as effective unless it happens to be very popular right in the area the device was lost.