Weirfan I was the same way, up until about 2 years ago. I live in an very low crime area, in a small tight-knit gated community, and I'd never worry about locking my car at night if left out in the driveway or turning on the alarm system, or even making sure all the doors were locked when we went to bed. But that all changed when someone came into my yard in the the middle of the night, and when I heard a noise and got up and looked outside I was greeted with a gun pointed directly at my face through the window. Luckily I was able to hit the deck out of sight, crawl to safety, and call the cops, but by the time they got there he was long gone. My wife was so shaken up by it that our whole family stayed at her mom's house for the next 2 weeks while I beefed up our security. I put up a dozen security cameras covering every inch of our property (the Hikvision ones linked to above - I LOVE them!), added glass break sensors & outdoor motion sensors to our existing alarm system, added alarm sensors on a few windows that didn't have them, put motion-activated flood lights on all sides of the house, installed double-cylinder deadbolts (they lock with a key from the inside) on all the doors with glass panes, and bought a gun. All it takes is one event like that to make you realize that things could have turned out a lot worse, and I unfortunately I don't think I'll ever go back to having the peace of mind that I used to. I don't even like being outside late at night working on my cars anymore, like I used to love to do. It sucks.
Getting back to the cameras, the way I see it is they act as a first line of deterrence - not defense, but deterrence. Thieves don't like to take risks, they want to get in, get the stuff, and get out undetected - and cameras pose a certain level of risk. They also let a thief know that you're serious about your security and that it's probably not going to be an easy score, so hopefully they'll just move on. And for me, they give me peace of mind because now if I ever hear a noise in the middle of the night, or get a motion alert from one of the cameras, I simply pick up my phone and look the grid of cameras to make sure everything is okay, and go right back to sleep. But other than acting as a deterrence, if you do catch someone robbing you on camera the odds of ID'ing them are very slim unless it happens to be someone you know or have seen around.