I recall either "The lock picking lawyer" or McNally explains that only in 3% of cases are locks picked during a burglary. In all other cases windows or doors are simply forced open. So at best locks are meant to prevent of crimes of opportunities.
If I can go out on a limb here, I also think I recall that they have very specific things they look for. For instance they will often run straight for the master bedroom and start pulling out drawers/checking closets because people tend to keep jewelry in there. They want small items.
Anything that slows them down tends to deter them even if they make an initial attempt
Oddly, this is a case where they would have had plenty of time to pick the lock as well, and it would have been much quieter.
A lock forces the thief to either spend time defeating it or physically break something. Even if it doesn't slow him down it should hopefully make it visibly obvious that he's doing something illicit.
You can spudger one of the glass units out and back in from the outside, without leaving a mark.
They look better than they are.
I have heard of someone cutting through all the plastic and pulling the glass out that way, though.
Both rather more obvious that surreptitiously jiggling the obscenely crappy Eurocylinder that the door came with.