Having managed a CCTV control room that was used for crime programme backdrops, featured in many news stories, was used to test new systems, and was generally state of the art for its time (1998-2006), I can throw some light on this.
Most of these poor systems are not regularly maintained correctly, many smaller/older systems still use VHS tapes. The tapes are often not cleared in a degauser so are taped over again and again. They only use one or two tapes and don't buy new ones very often. Also if the cameras are not focused correctly or are not being monitored, people often just move a camera to cover a different area and don't adjust the system.