Unless you are buying it doesn't really matter. They aren't your friend, they are someone who's job it is to sell you something. They have been trained that the success rate for a closed sale is greater if you act friendly. Some play the part, some don't.
I grew up in California. It could be that Californians just aren't as naturally chatty as folks in the South, and that is often interpreted as being unfriendly.
Which DVC staff are you referring to? We've had lots of fun talking the kiosk staff over the years. They seem to tickled to interact with someone who actually owns and enjoys DVC!
Strangely, we even did an add-on through the Disneyland DVC staff back in Sept 2007. We didn't expect to buy an add-on ... but oh, the incentive-force was strong that day. We were absolutely delighted by the CA Guide! So much so, that she talked us into an add-on that remains our largest single block of points. How did she do that? FWIW, my husband and I both still agree ... we prefer the CA guide to our assigned guide at WDW. (Sorry, WDW Guide ...)