I think this is really just a case of the bar constantly being raised, only to find we are now at unreachable levels.
For example, makeup used to not be standard for all women to wear. But once it did become standard, advertisers had to find some way to make their movie stars/actresses/etc look superior. Where to turn? Airbrushing. But soon everyone catches on and now everyone has some sort of airbrushed senior picture/glamourshot/etc. Airbrushing is now the norm. So if a makeup company didn't use photoshop, their product would seem inferior to "everyday life."
I mean, I could get upset with all the women who use makeup, effectively forcing me to waste an hour ever morning or resign myself to looking plain in comparison, or I can just accept that this is the way the world works. The plumage keeps changing, but we're constantly trying to find ways to make ourselves prettier/shinier/more than the next person. Once it catches on, something new will be found. Everything is fake anyway.
As far as whether or not it's rude, I have struggled with that. I occasionally do touch up our company "mugshots". We make them lose a few pounds, get rid of blemishes, etc. It does make me wonder if the subject would be offended if they knew, but I need a job so I do what I'm asked.