I know what you mean. I work with pretty much all the vendors, and I can say that you should just be happy you don't have a Ford Direct site, which requires you to pay a "SEO Fee" to just change title tags.
Anyway, if you install the "Redirect Path" plugin on Chrome, which shows when you get redirected on a site, and what kind of redirect it is, you will see that the link to your dealership page from one of your VDPs on Cars.com is actually a 301 redirect. Basically, they are doing their best to keep any authority from going to that page that would help the link back to your site. They also link to the www. version of your website, which then gets 301'd to the non www. version of your website. If, and how much, authority is lost with redirects is highly debated, but I usually go with a 10% loss of authority. Basically, any authority that the link might provide is greatly decreased by these redirects.
This is just Cars.com, but I would guess the others are similar. Do these links register in your Webmaster tools?