>OTOH, turning on the tracker ASAP gets you a location now, and that's something the police can move on.

Can you get a police response in time to move on that information? In the world of police response priorities, I can totally understand that a stolen vehicle (even with active tracking in progress) pretty low on the list. Active car jacking, send a unit to respond. Reporting a car theft from a shopping mall parking lot, send a unit when available.