Secured by a plate

Yesterday, while travelling home from Koeln, I noticed a hot dog stand at the departure platform in the central railway station. I thought about the fact, that it's not easy to secure this small hot dog stand and how they managed to do this. You can see the booth in the next picture.

After one minute of thinking, I noticed a little plate at the top of the window. It was so obvious, why should someone break into a hot dog stand, if there's nothing to get?

(Written on the plate: "Intrusion unprofitable, no cash available.").