but it just seemed that that was more emphasis being placed on what happens after the guys break in and not so much on keeping them out in the first place.
That's another assumption and you don't really know my reason for having things. The security system is primarily for when I'm NOT at home. Don't get me wrong, it's armed when I am at home. I'm not home much, and I don't really like the idea of anyone getting hold of my guns. I don't have the money for a full out gun safe. I have a lock box bolted down but it could be gotten into with enough time.
Thus enters the security system. The purpose of that is to severely limit the amount of time that anyone can have in the house. If you know enough about how alarms work, you will realize that they are FAR from full-proof... even a nicer system. The greatest tactical advantage to an alarm is to keep perps from knowing you have it. Trust me, I've installed them. The MCP is usually in a closet in a central location. Given that knowledge, with a 15 second delay on a keypad, anyone who knows an alarm is there can effectively circumvent it pretty easily. First they cut phone/cable lines. Then just kick in the door and you have on average 15 seconds to find the control panel and rip it off the wall before a siren goes off. Even if the siren is activated for 5 or 10 seconds, many neighbors would assume it's a false alarm. I've seen this happen on several occasions.
Now, if they don't know it's there they just kick in the door. All of a sudden this thing on the wall is beeping at them. There's that 2 or 3 seconds of "oh crap", and then they have to come up with a plan to circumvent the system AFTER IT'S ALREADY BEEN ACTIVATED. Before they get very far there's a siren going off. "Oh crap, what to do"... There's a much greater chance of them just running away. This is coming from someone with professional experience with security systems. Signs are good deterance against crack rock burglers. If someone has a personal vendetta, there's a good chance they'll enact that vendetta with or without the sign. The sign just gives them an opportunity to come at you with a plan.