As repetitive as it may be, I have to say it, having been constantly disregarded in a world that talks too much.
We aren't antisocial. Introversion is a personality trait. It's not shyness that one outgrows. It is definitely not a bad thing. It's a good thing rather. We notice things others usually don't, though we rarely say it out loud. For one, loud is never a word one would associate with us, unless you're talking about the inside of our minds, since very often we're deep thinkers. Overthinkers even. That's another story.
We collect memories. You could've said something in passing, something so trivial that probably you don't even recall, but if we love you, we remember.
We are great listeners. We are happy, and beautiful, and human, just like you.
Not everyone needs to be like my extroverted friend who sometimes talks to just fill silences or needs adrenaline pumping through their system with some outdoor activity or the other. There are few of us who, believe it or not, like being home, spending time with family, close friends, our pet and we don't have to DO SOMETHING to enjoy ourselves. There's absolutely nothing wrong with that. Everyone's got preferences. So be a grown up and respect them. Capisce?
FYI–Pointing out that we have been quiet and asking us to speak really doesn't help. It only makes it worse.
If you love an introvert, give them time and space. They will open up to you on their own time. And when they do, listen to them, because chances are they are sharing a piece of their soul. I cannot stress this enough– LISTEN.