Because it’s hard to investigate that with old cctv tech. Unless the person on the video was easily identifiable, it’s hard to do anything to follow up. With the new networked AI tech you could search for the person across the whole network to find out where they went / get a better view of them.
I would hazard to say that wouldn't have happened had a police officer been stood there instead.
Some major shops in the UK have photographs of police officers on the door, because it reduces theft!