More common than you would imagine I would say in rural areas where there are no cameras / never see the police, I even heard at work a few years ago about an old boy who trundled into town along the lanes once a week in his old series to do the weekly shop and had not been insured or much else for 40+ years, he never got caught, just told some family member after he had stopped driving in passing conversation.
It's like Hot Fuzz around here;
"Dunno what all the fuss is abount mind, I only uses her betwixt the fields and once a week fer shoppin' why wud I waste my money on that insurance makarky if Ise is careful loike"
Obviously a lot of rural seasonal "helpers" are the same, you can get a decent looking old banger these days for not much, and if you do hit someone, just leg it off across the fields as there will be no clue to the owner in the way of any documentation.
Biggest balls up ever was when they lost the tax disc and did not go the plate route, but put reliance on ANPR, which is great if the plate actually belongs to the car it is supposed to, or there were loads of traffic cars with it.
When they invent a camera that will catch pisheads, bad drivers, tailgaters, lane hoggers and all the main reasons for crashes, I will STFU.