Your correct, it happens daily and is very annoying. Especially when the property preservation calls you up and asks for a copy of the listing agreement, you send it, tell them that you and homeowner are maintaining property, then they still go to the property, see it is maintained but still change the locks and post a "we have found this home vacant and abandoned on this date" notice on the door for all the world to see the home is vacant and inviting break ins and theft of anything attached or detached. Hot button with me, can you tell?
I have seen several homes in my area that the banks have changed the locks on. Sellers really should be aware of the fact that this can happen to them and it can really mess up a short sale. I'm not a lawyer but one of my clients spoke to a lawyer after their locks were changed and the lawyer told them to just call a locksmith and change the locks again. I was actually surprised the lawyer gave them that advice.