The company I worked for bought only refurbished Dells unless a user need a special configuration. The IT guy said some failed the final QC, some were lease returns, some are contract overruns for places like Best Buy, government or corporations, others returned by buyers for other reasons and some were actually scratch and dent either on the assembly line or shipping to original owner.
They refurbs come with the full factory warranty and support. Since retiring we've never bought anything but Dell refurb or scratch and dent. No problems.