Why do men pretend like women they're not attracted to don't exist?

Why do men pretend like women theyre not attracted to dont exist?
I've noticed this a lot that men ignore me. They won't make eye contact with me, they will never notice my presence, they will never talk to me and if I talk to them they barely say anything. A lot of other unattractive women has told me that the same thing happens to them.

I'm not even trying to get with them, and it's not that I'm always interested in them but they don't treat me like a normal human being and it hurts my feelings honestly.

I never thought that I was that unattractive. I mean I'm 5'4, I'm not underweight or overweight, I have good hygiene, I have long healthy well kept hair, I have a good posture and so on. But recently I've just came to the conclusion that I'm unattractive because my sisters and friends get attention from men all the time. I will walk with them and men will be staring at them. And when I'm alone no man even looks at me.

Why do men ignore women they are unattracted to? Even when I asked for a guy at my school for a pen (which isn't something romantic) he just ignored me and pretended like he didn't hear me. And the girl beside him ALSO asked for a pen and he gave it to her.

I just feel so disgusting and unwanted, and I want to know why men do this.
Why do men pretend like women they're not attracted to don't exist?
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