This is a loaded question, but I will answer it with my personal view. I notice a woman's lips, because, if I have any hopes of kissing this woman, I want the kiss to be something memorable and exciting.
A kiss is something to stir the senses, and personally I find no stimulation from just simple mouth to mouth contact, but when lips meet, there is often an electrifying moment at point of contact.
In my case, my mind takes this two steps further. As a man, I can imagine that private intimate moment if we are making love together, that she might become playful and lower her mouth onto my private area,
but then there is also the fact or myth that a woman with thick lips for kissing will also have thick lips in her genital area too. This can also be something of personal interest to a man.
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