Whether they're fake or not doesn't make much difference. There are always going to be better looking people out there, so people (particularly girls) will always wish they were one of them.
In fact, the more fake they are, the more obvious it is to everyone that they're fake... so clearly they're not doing anything unrealistic -- unlike porn, where girls with small waists go around sporting massive breasts. Clearly advertising works within the bounds of plausibility, therefore the question of whether they're fake or not has no real meaning.
If they could be real people, then just assume they are, because if they could be, then the only reason they're fake is because it's cheaper than finding one that isn't. If you stop them using software to enhance people, they're just gonna have to do what they did before the software, and go out and be more selective -- which in turn will put more pressure on real models.
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Getting back to the point... if these people can be passed off as real, and they do indeed give you a boner, or they're being recognised as attractive, what's the issue? If they give you an image, and your biology says "me rikey a rot!!", whose fault is that?
Did those mean ad agencies re-wire your genetics? Does anyone even remotely believe that what's attractive to people can be prescribed? I know that's the party line, but guys, really... procreation doesn't work that way. You can tell me that cellulite is normal all you like, but that will never make me prefer it.
The quality of being attractive comes in many forms, and for many reasons. Most of those involve conversation or discovery... but an image won't go for coffee with you. An image must be purely physically attractive. No points from column B, just points from column A, nothing else!
This doesn't make Betty in accounting any less attractive. In fact because she's able to pull a little from column A, B *and* C, she might even be more attractive, which is the reason you have a crush on her, rather than just wanting to bend her over like that chick in maxim.
Again... that doesn't change the rules of attraction, it just means that advertisers need to maximise what they can achieve with only column A at their disposal.
They didn't force that into your biology, they're just concentrating the effect with the 'liquify' tool. You've been wired to react that way by your genetics. They give you what you want, even if in retrospect you really wish you weren't ruled by your biology.
Attraction -- though complex -- is hard-wired... if it were really so subjective and open to interpretation, then there's no way you could sell 50 million copies of anything, by putting jessica alba on the cover.
We're all more similar than we are different, despite what we want to believe... and we're all slaves to our genetics, despite wishing we could intellectualise it away.