I think the answer is different depending on why the warranty is missing.
1) the car is a salvage vehicle, buyback, or similar
2) a manufacturer decides to sell all of its cars that way to lower their prices
3) most units are sold with a warranty, but buyer can choose to delete it for a discount
I think I would be most comfortable with #3, and I would seriously consider doing it to save a couple thousand dollars. I am assuming this is a reliable model from a reputable manufacturer (for instance a Honda Accord), which are normally the only cars I shop for anyway.
You can think of a warranty as an insurance policy. Insurance policies are priced higher than their expected value to the consumer. So if you can afford to self insure, you can save money on average. Plus, warranties are very expensive to administer because you get all kinds of people wanting solutions to the most insignificant flaws like they think they heard a slight rattle once, or there is a tiny drip in the paint inside the trunk lid. And they demand a loaner car for those. That all gets priced into the cost of a warranty. I'd really rather not pay for other people's right to make trivial claims.