While it sounds like ignorance, all it takes is some bad experience for a shop to rule out a model of car. I went to a quick lube place over 20 years ago to have the oil changed in my old 83 VW Vanagon. Then one time I went back and they refused to change my oil because on some other Vanagon they didn't tighten the oil filter and caused engine damage. Besides the fact the wouldn't change my oil because of their mistake, I never got a good deal because they had a rule that they couldn't enter a customer's car for service, and in the Vanagon most of the service items are only accessible from the inside!