Why do people lock their luggage given the baggage employees and TSA can open the luggage?

They make TSA approved locks- which TSA can unlock with TSA keys (if you put a different lock on they can cut it off).. why do I always lock my suitcases when traveling with TSA locks?

1. it deters criminals from stealing items from my suitcase as well as the case(yes, you can slice a suitcase open, but the lock is just another step vs an open suitcase); also how obvious is it in the airport when someone grabs a bag off the conveyor belt and slices it vs taking it and unzipping it (if they just want to steal a couple of things from a suitcase and then toss it back on the belt)? Also after leaving the airport it deters would be criminals
2. the lock keeps the zippers together; and if TSA opens it they have to close it all the way to get the zippers together to put the lock on- no items falling out
3. if the case gets lost employees are less likely to rifle through it/airline employees handling the cases are less likely to try to rifle through it