Interesting thoughts one must say. Let me share mine.
Coming to think of it, the word advertising is synonymous with marketing and it's Advertising & Marketing that we hear all around. All for a reason. Without advertising marketing is a deflated balloon. For the balloon to be flush with air and to touch the clouds advertising is indispensable. Brand building (what marketers strive for) is possible only because marketers advertise. Marketing as a business manoeuvre has no solitary existence.
The case is different with Advertising, it can stand on its own leg. Purely because more than a mere profession that caters to business interests, it is more of an art form where creativity incarnates itself in vivid detail.
Thus there are two ends for advertising, to build brands for one and to achieve creative peak for another. And it's the latter that drives the admen, it's that for which they work actually. When the ad is creative brand building happens automatically.
Those TV commericials, billboards etc. all have the creative spark in them ( of course there are not-so-honourable exceptions). That's why as Asha said, they leave lasting impressions on the minds. To those people who skip them you indeed are missing some-creative-thing.
See some creative sparks at
http://www.adsoftheworld.com and I challenge you to skip this one
http://in.youtube.com/watch?v=w9qIssi2WuAAnd last but not the least, let's leave ETHICS out of the equation. Neither marketing has it, not advertising. The ethical eye is blind in business and it's two legs ( Advertisng & Marketing). To be ethical means to play second fiddle in this realm.
Nothing ethical about it, a nice caption for business, right?