alt Hacker NewsLocks raise the cost of bad behavior, which makes it less likely. They can still be quite meaningful to someone who breaks those promises, if that person doesn't have the tools or time to defeat the lock, or is just plain lazy.
I live in a pretty low-crime area. From time to time, residents complain about things being stolen from their cars. Every single time that I've seen, the cars have been unlocked. A thief certainly could smash a window to steal from a locked car, but the thieves around here seem to be opportunistic and won't go that far.
And a larger lock pick tool does pretty much zero in the case you listed as that is not opportunistic. Those are pretty much the open up and steal when they see an unlocked car kind of people.
It does nothing for the type of criminals that work in groups and steal tires of 50 cars at once, or whatever soup de jour of automobile parts they want at that moment.