Why? I finance every vehicle (okay, not the MJ) that I can, because my credit union will do 3.9%. The drawback is that I have to carry full coverage, but the benefit is that I have more cash in the bank each month in the event that there is an unexpected bill. At the end of the month, I use leftover cash to pay off things with higher interest- credit cards, extra mortgage payment, etc. When I got laid off unexpectedly a few years ago, I was glad to only have to lay out $92/month on a car payment until I got back on my feet. The cash that I had saved (and left in savings) was what paid the mortgage while I was laid off.
I am certainly not saying that it is a bad thing to pay cash for vehicles, but there are reasons to finance them as well.
I'm sure there are benifits to financing, but at this stage in my life id rather just do cash. i didnt bother to ask what kind of coverage i needed on the impala i got and ended up paying(with insurance) about 600 a month on that stupid thing. :doh: