I don't think the police started requesting camera footage of crimes from private citizens recently. It's just that they turned to businesses with security cameras.

I think realistically many people who own property cooperate with the police out of a definite sense of self-interest with no coercion required.

Police build little databases of where cameras are located and will use them to build timelines, etc. I served in a jury where the police were able to identify a hit and run driver who killed a teenager by knitting together surveillance footage from a bunch of cameras and establishing what cars were in an area in a given 5-minute window.