The situation with suppliers keeps shifting (because change is one of the few things we can be certain of in this world, the others being death and taxes, as Daniel Defoe, Benjamin Franklin and Margaret Mitchell - in Gone with the Wind - have opined), and the way of referring to them is in continuous improvement as well. Years ago, when a spade was a spade, suppliers were suppliers and were happy to be so.

Then somebody realized that some of them provide goods, but others services, and others construct things on a contract basis, and the title "supplier" might not be good for all of them. So the latter group were then called "contractors", and if they hired other firms to do some work, they were "sub-contractors". Then someone thought the general title "vendor" might well cover all these various providers (not bad - the "vend-" bit means "sell" in Latin and French, for example) - but new terms are not immediately used by everyone, and sometimes we see an atavistic return to the old familiar term, as in the Outstanding Supplier awards.