I feel that people invite me to their plans only when they accidentally mention them in front of me.

Months ago I was walking with a friend and his friend, which I've known for a few months at that time, definitely not close, she's just an acquaintance. She mentioned her b-day party next week, then invited me. I knew that her b-day was coming but I was expecting not to get invited, simply because, I'm not close with her.

Another example I can think of was when I was with this close friend and his other friends (again, they're acquaintances to me), and they mentioned a road trip, and again, they invited me.

I don't know if I'm actually liked or they didn't want to be rude. I can't be sure cause I'm rarely asked to hang out. I'm always the one initiating. Even sometimes I'll ask if they got plans for Saturday night, and they'll say "yeah". I mean I was making it pretty obvious that I wanted to hang out, and I was expecting a "yeah, come at my place at 9pm", rather than just a "yeah".