If you don't have insurance for the car before you register it at the DMV, they never know that you don't have insurance and you could drive without getting a letter.
I believe they only know that you don't have insurance when you lapse or cancel you insurance, if you had insurance from the get go before you register it like you are suppose to do.
If you lapse or cancel your insurance then your insurance company is required to let DMV know that you do not have insurance from them anymore. Then DMV will will send you a letter if they do not get info that you have not insured that vehicle.

Yes this happened to me. I bought a car at a private dealership and told them that is was insured even though it wasn't. They gave me temporary plates to drive off the lot. then I went back to the dealership and got the real plates that DMV sent them to replace my paper plates. I drove for 3 years while not having insurance and not once did i get repercussions. I decided to get insurance for the car since I had the money and had insurance for 6 months. Since I got another car I put this one in my garage and did not continue to pay for the insurance for it since i was not driving it. 2 months after not paying for insurance I got a letter from DMV sating that that I would have to pay fees and fines and that my license will be suspended. Well I disputed the charge since I was not driving the car on the streets. I had a telephone hearing with DMV stating why I should not pay the fees.
DMV went in my favor and decided to waive the fees/penalty's and suspension of licence under the condition that I return the tags and plates to them.
So I returned the plates. I could have still been driving that car if i did not get insurance for it after I registered it at DMV.
The only issue I see is if you get into a wreck, obliviously. If you get pulled over and a cop ask for your insurance card. But most of the time I get pulled over I don't get asked for insurance. Just title and registration.
Maybe I was lucky.