If locks work why do we need alarms?

Because a lock only keeps an honest person being honest. If someone isn't honest, they will defeat the lock. That is where the alarm comes in, some don't really care about the alarm, that is when the police get involved. The problem with the police is that when seconds count, they are still minutes away. I was reading an article about police responses, it said the average response time for law enforcement officers was between 25 and 30 minutes. If you were in a very rural area, it could be as much as several hours.

alarms and locks are good at keeping honest people out. LOL a skilled criminal can get in.