Alex,
Several others have touched upon it... Internet shoppers are just that... they are shopping on the Internet... then they hit dealer's websites and are instructed to call or email.
When they get responses, then they encounter various processes designed to get them in to the showroom.
"Is this as good as vehicle shopping on the Internet is going to get?"
"Are 3rd party services like CarsDirect and ZAG going to disintermediate car dealers?"
As you observe, consumers are realizing that the bloom is off the rose of Internet lead submissions in terms of receiving a better buying experience.
So if the Internet lead submission strategy with exceptional followup efforts, processes and Internet Managers

will not be long term solution, what is?
The owner of this blog suggested my company's service may be one answer. We have a hybrid approach. We have a consumer-facing Desking + F+I system for a dealer to add on to their website. It is a hybrid approach since consumers have to verify their email address in order to get in (so you get the selling opportunity regardless as to whether they buy direct or not).
It hasn't disrupted website lead volume one iota, so it is therefore capturing the consumers who weren't submitting leads before. Dealer experience is also that the unsold consumers respond better to dealership follow up efforts. Lift comes from unsolds who buy + those who buy direct (and yes, some have).
But this isn't an infomercial. My company's hybrid eCommerce solution for a dealer is only one idea. If the lead model is declining in its effectiveness, what else will be effective? What is it that the consumers really want?
Build your car, name your price?
Trade appraisals?
eBay listings?
Live Chat?
I believe that today's Internet sites are little more than advertising billboards since all "selling" occurs in the dealership... which is NOT what consumers want. I think that is your "WHY" Alex.
So what do we think can be done about it?