Cameras don't phone home regularly (some nowadays have WLAN, but far from all, and it is mostly for communication with a phone), so there is no good way to get a lock-signal to them without adding a mechanism extra for that. Offline schemes with timeouts or something still have a risk of going wrong.

Professional photographers have insurance, so most of them probably rather would loose a camera than having one lock up by accident when needed, or any complications added to robberies.

Right now, at least some the large manufacturers don't even have registries for stolen devices in case they turn up or get sent to service, that's something that could be improved easily.