Low mileage daycabs are not that uncommon.  Lots of jobs out there that use a tractor for a couple hours a day, or travel at slow speeds in stop and go traffic.  Lots of them are worn out far beyond their miles, also, but there are some gems to be found.  We have a Volvo which was owned by an electric company which had  350k when they sold it @ 12 years old.  It's a good truck, just "stood by" a lot.