Breakins have been around since bewfore I moved here and in the past it used to be the gy[sies. Iremember my kids bikes being stolen from the front garden when they had left them to come in for lunch. Opportunist but we reckon they had been watching us and the bikes were quite new – xmas pressies from grandparents.
A dog definately keeps them away – its the noise alerting anyone and with our dog , apart form the bikes we never had any problems.
I know may who have been broken into – a lot are holidaymakers just arrived and leave the door shut but not double locked – easy to slip open with a bit of plastic. And the same as you Frank – not changing the keys when everyone has had access to the place!