CCTV doesn't work well when people feel like nobody is going to bother to check its footage (e.g. pocketing a $2 drink from a big-box department store). But when it comes to homes, there are much higher chances of captured footage being used and examined, so it may cause opportunistic burglars to look at other houses instead.
Just because something doesn’t work 100% of the time doesn’t mean it can’t be effective.