I've been the victim of property crime 4x in the UK, and 3 of those times the entire thing was caught on multiple CCTVs. But that didn't help me get my stuff back or prosecute criminals. The one time I did get my computer back was when the police raided a stash house (due to an anonymous tip, not surveillance) and found a treasure trove of stolen electronics, which included my computer.
But having cameras everywhere in London didn't help at all, so AFAICT they only exist to surveil you.