That is true, if you feel the need to switch a car every 3 years (yikes) the least crazy route would be to lease. A lease can be negotiated just as easily as buying; the dealer makes the same money either way.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!

I don't know if leasing is slightly less stupid than financing under those conditions, but buying a new car every three years makes no sense unless you are liquid enough to pay cash. Leasing simply introduces a third party and reduces your down payment; someone else to profit off the fact that you are buying something you can't afford. Borrowing money to buy/lease a depreciating asset is a great way to reduce your net worth.