It's also impossible to do your best SEO work for more than one dealer, with the same make, in the same DMA. All that does is drive up the PPC costs for shared terms.
I believe a major problem is hands off dealer owners who delegate their business operations to GMs, GSMs, ISMs, eCommerce Directors, or others and these people are not "in the weeds" business builders. They rely on companies like DealerTrack/DDC, most whom never sold a car, let alone online, to do all the work for them.
They generate mediocre (relative to what could be achieved) sales results and everyone is happy.
One question dealers need to be asking vendors is "How are you going to help me dominate, not just compete, in my DMA?"
Don't look to enterprise vendors to drive innovation, all you can ask them is "please don't suck"
-Geoffrey Moore
Author, Crossing the Chasm