In the U.S., the main deterrent against robbery is jail time. Most houses can be broken into with an elbow. Locks prevent silent entry and make it slightly harder to break in, they don't secure anything.

This. Locks keep honest thieves out. I don't know of any house that I couldn't gain entry into in a few minutes, without damaging anything, including my own.

Without damaging anything? Do you mean lock picking? Or you live in a neighbourhood where people leave their doors open?

No, it's often much easier than that. I do live in a pretty quiet neighborhood, but that's not what I meant either. There are a couple of things. One is that people tend to be vigilant WRT their home's primary access, but pay less attention to side-doors, back-doors, garage-doors, and windows. So you can often find one of these left unsecured. The second is that the latches on windows are notoriously bad WRT their ability to stay closed. They can often be dislodged by just bumping them gently while applying pressure in the right place, even when installed correctly. If they were installed incorrectly, or just carelessly, or if the house has "settled" windows can be even easier to defeat. Another weakness of windows is the glazing, sometimes it just slips out, or can be easily pried loose, sometimes it takes a screwdriver. Until very recently, little attention seems to have been paid to the security of windows in residential construction. There are a few other more-foolproof entry methods that I know that do little or no damage, but they aren't the sort of thing that a burglar would do.

PS I learned most of this at Texas Fireman's Training Academy (and just paying attention to my surroundings), in case you're wondering.