Amen

Or... maybe we just enjoy spending time by ourselves even if we're surrounded by good people.

Or maybe we are anti-social and are happy with the friends we have?

Or I just like peace and quiet. If I don't have something to say, I won't talk much

Being introverted isn't the same as being anti-social. You just have to get me in the right group, and I can be the life of the party.

Not really. I feel like it requires effort to talk to people. I can't be asked to make effort all the time. I'd rather spend my energy on more useful things

I'm pretty much all of the above.