the officer knows if you have insurance as soon as he runs your plate.. giving you a ticket for failing to have a slip is just an excuse to give you a ticket.. if you actually didn't have insurance, the ticket you would be receiving would me MUCH worse..
Actually, as the insurance is with a private company, police aren't provided with the status of your insurance when they run your plate. At least not in Ontario, Quebec (and I'm sure others such as BC with government insurance) DO provide this info to police.