People would think security camera usually do not worth buying, because dangerous things or incidents of emergency seldom happen. And they think cameras dont help at all.
But they forgot one thing that IF something really happened, security cameras footage might be the only prove and clue that you have. It does not catch the thief of burglar directly, but you have a bigger chance to know what the situation is.
People also use cameras to do something else. To find their keys, wallets. To surveillance the baby room without entering it.