It will marginally help keep the 'honest folks honest', but as Joe mentioned, if they think there is some fast cash in there all locked up - they will do what is needed to get into it.
Last year my old Club did an overnight in a protected campground/cabin facility on an E. Texas lake. Everyone that left their tackle 'locked up' in their boat that night, had nothing to fish with in the morning. When I was doing T's and traveling around the Carolina's, I ALWAYS took everything in.
Tex