Making potential intruders uncomfortable. The whole point of protection isn't to stop burglars, as there's no such thing as an impenetrable house, but to delay and discourage them so that they will rather try the next house or, better, move to another area. It may seem harsh, but that's how it works. Surveillance forces them to wear masks, park their cars far away, etc.

Regarding HikVision cameras, they're closed and untrustworthy just like every other brand out there; there's a huge list of compromised cameras, and only some of them were from HikVision. I wouldn't feel safe with any camera that I didn't put behind a physical separated and firewalled network that I would access only using Open Source software (read: no proprietary apps).