Before I was a camgirl, I was a professional boudoir photographer and retoucher. I both took photos and did hundreds of hours of photoshop work on them, sometimes pore-by-pore redrawing. That shit is tedious.
Anyhow, if you put on makeup, you're trying to make yourself look more beautiful than you are. If you position yourself just right in the light, you are picking out a moment of time where you look gorgeous. Even with no photoshop retouching, the correct camera, lighting, pose, and makeup can make you look a thousand times more beautiful than you "really are." And for some reason, we consider that to be okay, but photoshop isn't. Photoshop is just one step further. Maybe in the future we'll develop supermakeup that gives you a perfect complexion, and contacts that make your eyes clear and bright. Would you reject using that?
Extreme photoshopping is used to pursue an ideal beauty. Usually the most extreme photoshop is used in cases of art - fashion magazines, or people meant to symbolize an ideal, not someone you recognize. If it's a well known character or celebrity, photoshop is used more similarly to makeup or an alternate world where they worked out and lost weight.
Everybody wants to look beautiful, and photoshop reflects what we could be, not what we are.