E3 has more in common with animated movie production (think Shrek, Monster's Inc, Dispicable Me, etc.) than game making. They take scripted actors, scripted scenes, and scripted events and make them play out in a very limited way. This makes it easy to test which translates to making it easy to make look pretty. Once you enter an unscripted player into the same environment (actual game development), the player will quickly discover that there is nothing around a lot of the corners you see in the movie, that you can't run it at acceptable frame rates without a beast of a computer, and that the further you deviate from the movie's intended path, the more likely it is to crash.
My point of all of this is that no one should ever assume anything shown at E3 is remotely playable unless there's a system sitting there where anyone can play it. Ubisoft showed a movie production at E3-2012; they showed a game production at E3-2013. If they showed an unpolished movie at E3-2012, there probably wouldn't be half the interest there was in it at E3-2012. E3 is intended to showcase products, not show what early development stages of games look like.
I can see where you come from, and the metaphor is apt. At the same time, I cannot buy into the logic.
This is like going to a car dealership, putting money down on a Corvette, and discovering that the car you actually put money down on was an Audi A3. If the car demoed on the show floor was a Corvette, I'd be disappointed when I got my A3. There is no excuse that would allow the A3 to be acceptable once the dealer had my money. The A3 isn't a bad car, but it wasn't what I put money down to purchase. The real problem here is that Ubisoft demonstrated a Veyron here, started to back-pedal and call it a Corvette, but based upon current language are actually delivering the A3.
This cuts back to the whole pre-order culture and how much people are willing to invest into a game sight-unseen. We run into problems again and again, in which a complete lack of demonstration would have been better for a product. Actual demonstrations of what a product "could" be are taken as demonstrations of what a project is, something that should be a foregone conclusion. Consumers start buying pre-orders for the things they saw, and are delivered something else. Consumers raise their ire, developers say too bad, the next games developers make have smaller pre-order numbers, publishers say developers are a liability (after they pumped pre-orders by requiring non-representative demos), publishers kill developers or force them to work on formula games, and games become risk-averse generic clones of whatever is popular at the time. It seems odd to link lying to degredation of an industry, but the video games industry is caught in a vicious circle of lying and back pedaling in order to meet unreasonable sales goals.
To answer your metaphor, I offer you an anecdote. I went to see the "comedy" Bad Teacher. About 45 minutes into the movie's running time I got up, walked out of the theater, and demanded my money back. The movie hadn't made me laugh once, and I couldn't sit through the second half of the movie. That comedy did not live up to expectations, so I demanded my money be refunded. The movie theater did so gladly, and I was back the next week to watch a different movie. If I were to have pre-ordered Watch Dogs, I could not get my money back after booting it up and discovering that advertisements did not match reality. I couldn't even get store credit from most brick and mortar stores. I will have paid 10 times the price of a discount movie ticket, for an item that was sold to me via lies.
As much as I hate to admit it, a movie can be walked out of. Gaming has removed the ability for consumers to return products, while pushing people to buy the same products without any background. Those rare instances where something is known are eclipsed by PR teams pumping out demos that don't really represent the final game. Lather, rinse, and repeat. With the inclusion of pre-order bonuses, more people are tempted into buying games with no method of responding to ones that wind-up being of poor quality. It will take either a concerted effort by the masses not to throw money down on pre-orders (unlikely), or a collapse of the gaming industry (sounding more likely almost daily) for publishers to realize that these practices are toxic.
*Please note that I chose the references to publishers and developers in the above statement carefully. Developers are largely under the yolk of publishers when it comes to some of these practices, though they are not without blame. It's, in my opinion, Publishers that are cutting off their noses to spite their faces.