How true: locks keep honest people from taking things. Over the years I noticed that when I frequent my local bike shops, I just place my helmet over the mirror. All other riders have been respectful of that.
Whenever I go in other shops, I have always locked my helmet to the lock by the rear rack. I have from time to time, juggled two helmets onto that single click lock.
I have a UClear system on all my helmets, so I wouldn't leave a helmet locked to the bike over night, but for a dinner stop or a movie it has worked great.
So I have looked at my locks as a reassuring device that offers me a sense of security. Locks keep honest people out, but crooks will always find a way. I consider myself fortunate to be one of the many riders who respect others and their property.