I'm pretty sure that most luggage is lost when connecting at a busy airport, and there's some kind of glitch in the baggage handling at the airport. It's doesn't have to be a system-wide failure, just a single truck-driver running late, because a loading-team is two down because of the flu, and 100 bags miss their connections. Naturally, they are given lowest priority (when running behind, better get as many bags as possible on the right flight in time - whats it worth moving one bag that's already missed its flight, instead of one that has a chance of making it).

The bag lie around until evening when the pace slows down, and the remaining bags are routed to the relevant flight. But it might be a while until a there's flight in the relevant direction, and there might not be enough room on it.

At the destination airport, the bag waits around for a courier pickup, and that might take a while, because the airline wants to get as many bags as possible on the same pickup, because it's cheaper/easier.

I may be mistaken, but I'm pretty sure: At NO point during this process doesn't the airline know exactly where the bag is. Barcodes are not at fault here, RFID won't fix it -- the problem is overloaded systems, delayed flights and overly optimistic connection-times are.

They don't tell you this, because it's simply easier not to. If they telling you one thing, they'll soon end up rationalizing every single decision they take regarding every bag to everybody. It sucks but the alternative sucks more.

Upgrading baggage handling is expensive, and there are only the carriers, which in turn means the passagers, to pay for that.