Girls have a super power they can use to live rent free in any guy's head pretty much eternally. All they need to do is catch them off guard with a compliment.
A guy will keep a shirt until it literally disintegrates if one time a girl said "that color looks good on you." Pretty much every guy that wears a particular cologne, wears that cologne because at some point a girl said he smelled nice. It's not even a horny brain thing I don't think. It's just that guys get so few compliments on their appearance that every single one is massively precious to them.