Probably if they had an alarm they would forget and have the alarm going off a weird times.

Maybe they have but cannot remember the the password or numbers.

Or maybe like me nothing of value to steal.

I think houses with alarms in them are in a minority and not everyone has or wants one.

I think the sleepy village syndrome may have had something to do with it.

No problems for decades and then this happens.

My alarm is an organic canine smart alarm:)

It can differentiate between normal and abnormal intrusions. It makes a reasoned assessment over whether to awaken the house or not (usually goes for the latter option for good measure). It can automatically detect when an aggressive (bark) or passive (waggy tail) stance should be actioned. It also doubles up as a waste food disposal unit, keep fit coordinator, and a comfort blanket.

Unless an alarm is monitored then the usual reaction to a burglar alarm sounding is annoyance at the noise of yet another false alarm.

They almost certainly would have had at least 2 zones within the house, upstairs, downstairs as walking around eg to go to the loo would set the alarm off.

FE has already pointed out some of the reasons why they didn't have an alarm. Note also that a neighbour now say they will the lock the doors. This indicates that it is not normally an area of crime.

"Why no alarm on this house?"

Probably the same reason as there is not one on my house.

Older folk tend to waste their money on heating and eating!