I think the idea is that the siren will make the burglar run away without taking anything. Also, I know that at least some companies have the alarm system connected to the smoke alarms and will notify the fire department if there is a fire (helpful if the fire starts when no one’s around). I haven’t looked into this, but having an alarm might reduce the price of home insurance. If the cost of the alarm system is less than the difference in home insurance prices, it would be worth while.