I wonder if car advertising is really necessary?

The amount of money spent by car manufacturers on advertising boggles the mind. According to their 2013 annual reports, GM spent $3.1bn on advertising alone, and Ford spent $4.4bn (their annual reports can be found on their corporate websites). That's billion, with a "b". Those budgets do not include trade shows - that's just media advertising on the internet, hard copy and TV/radio.
I'm not sure they need to be spending that money. Think about it. Most people nowadays are internet-savvy. If you're looking for a new car, chances are you're going to hit up a car comparison website, or visit the corporate websites to download PDFs or play with their car configurators. You probably already have some idea of what it is you're looking to buy, either from seeing them on the street, or talking to friends. Not once in my illustrious position as a consumer have I ever been swayed by car advertising. I've never been looking at Brand A, seen an advert for Brand B and swapped paths. I don't know if that makes me odd, or if that's the norm, but speaking to friends and colleagues, anecdotal evidence would tend to suggest that's how most people are.
When shopping around for my current car, I test-drove vehicles from 5 different competing brands before settling on the final vehicle. The decision was made on how the cars felt to drive, how they looked, and hundreds of other intangible things I learned from putting my arse in the seat and driving them. Advertising contributed exactly zero percent to my decision-making process.
Take the current crop of Chevy ads, for example. The cars they're advertising are - to be honest - total shit piles. I've had most of them in rental car fleets over the last year and there's not one I'd actually buy with my own money. Yet if the advertising is to be believed, they're so popular and so amazing that I'd be lucky to own one because the supply of unicorns they're made from is drying up and there are queues 500 people deep at all the Chevy dealers in the country.
Car manufacturers need to treat their customer base as adults who are capable of making informed decisions without the torrent of effluent that pollutes every form of media. At the very least they need to have some truth in advertising. Next time you see a car ad on TV, pause it at the beginning and read the fine print. Apart from the obvious "trained driver on closed course" disclaimer, you'll see something talking about how the model shown is not one that's available for sale in your territory. (In America, it means they're showing the European version of the vehicle). These disclaimers will be along the lines of "European model shown, not for sale in the US", or "Shown with optional LX accessory pack, not available in the US". So even if you were swayed by advertising, what they're showing you isn't something you can actually buy.
At which point I ask again - why spend $4.4bn lying to the public and treating us like children?