Many if not most equipment and car dealers have zero down/zero interest financing programs on right now on new equipment.  With interest rates as low as they are these days it may make sense to use someone else's money now and pay the new price off over 3-6 years.

PS Maybe the previous owner had a sand or gravel pit on his farm! Or was not the first owner - usually it's the first owner or lessee that runs the crap out of a machine for 500 hrs and never even checks the oil, then turns it in or rolls it for another new one. The later owners end up paying for the first guys free ride.