If women weren't so damn forgiving of slobbiness, if they weren't prepared to look for the diamond buried in the rough of a man's beer-belly, men might have to shape up a little. The only reason gay men are - on the whole - better turned out than straight men is because they have to appeal to other shallow, beauty-obsessed males to get laid, find a mate, etc. The corollary, of course, are lesbians. Now there are many glamorous lesbiterians, but even the most enthusiastic Sapphic-lover will have to concede that many are not exactly, shall we say, stylish. The reason? They don't have to be to attract other women; and since women find monogamy easier, they also slide into the I'm-married-so-what-the-hell-have-another-pretzel syndrome. When straight women really do insist on only dating hot guys, men will shape up. Until then, it's hopeless.
Sullivan makes more sense than Kipnis (and is also much more amusing to read). Both observe that there is a disadvantage to women rooted in the different attention men and women pay to beauty, and neither has a solution.
Feminists like Kipnis tell women to stop concerning themselves about their physical beauty and accept the consequences. Women who take her advice and let themselves go will be less competition for the women who still try to look good. By the way, Kipnis herself looks great and wears plenty of makeup. The competition among women will continue, and those who took Kipnis's advice will just lose in that competition.
Sullivan would have women insist that men uphold higher standards of beauty themselves. Again, the women who take the advice merely remove themselves from the competition: there will always be another woman ready to accept the man with his faults. The competition for men will continue, and those who took Sullivan's advice will just lose in that competition.
The problem of women having to put more effort into beauty than men do is thus heavily reinforced and not susceptible to easy dismantling. You can't explain a reason for it and persuade people to see the light and thereby solve the problem.
Oh, did you want me to solve the problem? My solution would be very non-grandiose. Women should continue to concern themselves about how they look, but without overdoing it. You don't need to buy expensive products or spend a lot of time using them. You don't have to drive yourself crazy comparing yourself to everyone else. Just take reasonable care of yourself. And let men do the same. Women could be a little more in touch with the fact that men who don't take care of themselves aren't attractive. Maybe if people behaved a little more sensibly, some equilibrium between the sexes could be reached.
UPDATE: Judging from the email I'm getting, there are a lot of men who think that nature created them to want to see beauty in their mate, but that women lack the same desire. I recommend looking critically at beliefs that are that convenient. You may think the woman doesn't mind or doesn't notice, but I don't. A woman may be willing to accept less beauty in return for economic security, but that doesn't mean she lacks the appreciation for beauty. It just means she appreciates the money more. You could also compensate for lack of looks with great sexual technique or witty conversation. But then, couldn't she compensate that way too?