It's true, they don't.
Person A walks along and sees person B, person A thinks person B is ugly, then person C comes along and thinks person B isn't ugly. Just because one person sees another as ugly, doesn't mean the next person will see the same.
Also beauty magazines don't help, they fill girls heads full of bullshit, telling them "You should be doing bl;ahblah to look good for men cause this is what men want" bullshit, I want a real woman, not one with more colour on her face than a pack of crayola crayons, or fake pointy boobs, or surgery to keep their face looking young, I want real women. I think the only reason some girls feel ugly is because of these girly magazines driling it into their heads that they are.
Unbeknownst to most men, we face the same perils, too.
Right now you have some people out there who think that masculinity and manhood is under siege, and so the war, they perceive, is one about controlling the spirituality of men. Looks, work ethic, and basic physique appear to dominate that concept of "spirituality", while the concern that gender roles are being blurred, thus appearing to eliminate the necessity of the provider male archetype, is another focus. While they might be right that our gender roles are being blurred, it's frequently for the right reasons. For example, instead of the idea that men cannot be separate of the typical, post-world war two era conflation of how tribal, Caucasians used to live back in the day, we've now come to embrace that all genders and sexual orientations are capable of accomplishing the same level of success, and if not, should be able to do so. And so the meme continues with some of these worry wort's, that if you're ugly, if you're not economically successful, or rippling full of muscles, or some anti-social, counter-culturalist asshat, you're a part of the problem that contributes to that level of "distortion", and thus a threat.
What really bothers me is how even the manly men of our society reject people who happen not to be physically perfect. Men hate body hair now, because they're dead set on reliving their lost middle school or high-school years while at the age of like, fucking fifty. We're taught now as men that if we're not as superficial as the egos on UFC, or the cover of a fitness magazine, we're not men. Fortunately most people don't follow that model, but the fear of actually being something other than the status quotient is continually reinforced at almost every level. I'd hesitate to say I'm a Person C who isn't always aware of when he's acting like Person A, or that he's the victim of want and need, like person B.
And I'll admit where I am superficial. I'll see someone whose not dressed like me and wonder, "Why's that?" I'll make the effort to understand them and I genuinely like to. However it's still a matter in my mind. I'll shallowly think how will others see me if I am with this person? I'll see someone whose not my version of "attractive", and the same problem rears it's head. I'll force the effort to correct that belief if it's not a natural one, and I genuinely like what turns out. An argument to genetics notwithstanding, the thing that brought me to knowing where I was flawed was a study about how racial divides are actually a matter of kin selection theory, and that we tend to preference members of the same race out of an inherent need to preserve "us" versus "them".
While not widely popular, it just reminded me about how false I can be sometimes, especially as it concerns "ugly" versus "pretty".