"I don't like people." - me
Conversations wear me out. I can do it, I'm not socially awkward but I'll never seek it out. The one trick I've learned after years of nonsensical drivel and small talk is to ask questions, lots of questions.
Everybody has something interesting to talk about, it's just a matter of finding the thing. Most people don't even know what that thing is, poking and prodding about past history, current interests, jobs, etc... will eventually bring it out. I'm not even attempting to find a topic interesting to me. As a geek I can find value in most topics as long as the person has intelligent, meaningful, well thought out opinions or anecdotes about the subject.
Fine, great, that's a cute trick for parties and such but how do I avoid people in day to day life... well it's almost impossible unless you have enough money to pay people to do all your social interactions. For the vast majority of us this isn't practical so we cope.
Avoiding eye contact, giving short answers so it doesn't lead to longer conversations, acting ambivalent, all ways of "dealing" when out and about in the world. So you come off as a rude, unconfident asshole - oh well, at least they won't try to talk to me.
Small talk is supposed to be a polite, socially accepted way of greeting people. I hate it, whoever decided this is 100% an extrovert and would go nuts without interaction for 5 minutes. Seriously, the weather, who cares. The price of petrol, blah blah blah - just say hi and go on about your day if you can't stand being quiet. But, because you can't shut up doesn't mean it's acceptable to force me into conversation. I counter making small talk with an introvert is just as rude as not answering the 1 millionth "How was your day?".
Introverts, like me, are worn out by any sort of social interaction. Even if we enjoy it, it's still draining. Poker night with the boys, great, but draining. I'll need a day or two of chilling to recharge. It's not that I don't like you, it's just me. This includes family time as well - as much as I love seeing family it's the talking I can't deal with.
Meetings, oh glorious meetings, crafted by people who like to hear themselves talk. The bane of the introverts existence in a workplace setting. I'll agree that 3% of all meetings are needed, the other 97% are so the extroverts don't get bored.
Anyway, extroverts are great, just carry-on talking to each other and leave me out of it.