Granted, registered cars are stolen all the time, but the question is, how many more auto thefts would there be if there was no way of proving who the real owner was? Of course there are other factors in play in that analogy, such as the relative return on a stolen car vs. stolen bike, ease of stealing, etc.

By a similar analogy, a locked door (or alarm) doesn’t prevent all burglary attempts, but it likely prevents some.

Programs like this work best when it is known to the criminals that almost every item has been registered, so it’s just not worth their time (or risk) to find the relatively few that are not. At the very least, if not registering, please record your serial numbers and make/model of everything you own. Even the smallest, cheapest thing hawked at a pawn shop can break a case provided the owner is able to provide that information at the time of loss.