Security cameras aren't perfect, there are a lot of variables associated with operating and using them. As an operator of security cameras, you have to pay for storage space of the videos, essentially, how long are you willing to hold onto the security videos? Keep in mind that audio files are nearly the same file size as video files. So most of the time, audio is not saved along with video. Then, as an operator, you have to maintain the cameras, keep them repaired, updated, clean, and manned. With all of those variables addressed and accounted for, there are still a number of obstacles as an operator, such as sun glare, weather, capturing an event in frame, having the event in focus, and keeping the lens clean.
As a regular everyday person, who certainly does not worry about one's security camera system. God forbid something happens to you, assuming you are even in an area monitored by security systems, and all the aforementioned variables line up. You still need to find out who owns the cameras, and ask them for the video files, with a pretty specific timeframe to have them look for. All the while you are fighting the clock before their internal storage deletes the files. If all of that isnt enough to have going against you. You are not entitled to any videos that are recorded by the business, as it is considered property of the business. Meaning that after you request the video, they can even choose to delete the video if they want to, and this is all completely legal.