that's the argument I always make to my wife about most make-up, definitely having her nails done, and the time and attention that she spends getting dressed. Most men literally don't even notice, so it must be to impress/threaten rival women.
I agree...with the risk of sounding outrageous I'lI say women "struggle" more to impress other women rather than getting the attention of men...whether this is conscious or not.
"Ah, those endless forests, and their horror-haunted gloom! For what eternities have I wandered through them, a timid, hunted creature, starting at the least sound, frightened of my own shadow, keyed-up, ever alert and vigilant, ready on the instant to dash away in mad flight for my life. For I was the prey of all manner of fierce life that dwelt in the forest, and it was in ecstasies of fear that I fled before the hunting monsters."
Jack london, "Before Adam"