I have bought used laptops (not from an official program like Dell Refurbished, though)— I would advise not to care what operating systems or drivers may or may not be on it, unless that is part of the deal, since you will be installing your own anyway.
I have also decommissioned machines, in which case the storage drives were securely wiped, meaning there should be nothing on them.
If you are installing Windows, a lot of drivers are available via Windows Update, so it is not always necessary to find each and every one on the manufacturer’s web site.