Most people round here lock their gates to protect their livestock against being let out, or even stolen. And the empty fields are locked to stop gypsies camping there - they were on the local common right next to the golf club for two weeks, and council had bother evicting them. I drove past at the time they were due to leave, and the council had got all the local farmers with tractors ready to pull the caravans on to the road. But gypsies know the law and how long they can stay, and moved off themselves.
So, I suppose locking gates prevents bother like that!!