This is true, but if you plan to drive the car into the ground, the loss in value isn't quite as important as if you plan to sell the car in a few years. I admit to having bought three new cars in my life (all the rest were used), and I guess the control freak in me likes to know everything that was ever done to my car and how it was driven. It's irrational, but that peace of mind is worth a few thousand dollars to me. So I prefer to buy new, but I keep the new car for at least 10 years. I drove my last new car, a Honda Civic wagon, for 402,000 kilometers before I sold it to a family who drove it another 160,000 km before they sold it on to someone else; I currently drive a Toyota Matrix that I bought new with cash, and am aiming for roughly the same ballpark km before getting rid of it, although the body might rust out first.Brand new cars.
(One of the few commonly-purchased items that I can think of which drops thousands of dollars in value the instant you drive it off the lot.)
I had bad luck with most of my used cars, and eventually calculated that I had spent more (cumulatively) on repairs than I would have spent on a new car.