Why is it so hard for people to accept when I say no or show no interest

Yesterday I posted here about not wanting to attend my neighbour’s birthday party and asked for advice because I didn’t feel like going. People suggested I politely decline, which I did.

I told her I had an upcoming exam (which is true) and she said it was okay and that she will bring food tomorrow , but I also got my period and wasn’t feeling well or able to focus, so I just stayed in bed. I’ve already declined several of her invitations before, though I’ve accepted some in the past.

, she showed up at my place with food. When she saw me, she asked things like, “Were you sleeping?” and “Don’t you want to spend time with us?” I apologized for not coming and for not having a gift. She said it was okay and that I could still come if I wanted, even though I had already declined. She also seemed a bit annoyed

She later said she would bring cake as well, which I told her wasn’t necessary, but I thanked her for the food.

I just don’t understand why some people can’t accept a “no.” If I’m not interested in going, then I don’t want to go. It feels similar with my dad if he found out I didn’t attend, he’d get mad too. Why is it so hard for people to respect that?