I've known people that have made it into their 30s (or, in an extreme example, early 40s, god forbid) before they entered the workforce, for a variety of reasons. Social anxiety is usually the reason that keeps people locked on their own little island; unfortunately, you can't overcome this feeling without facing it... every time you back down due to your fears, they gain a little bit more control over you.
My first job was actually at a burger place, and I was terrified of dealing with customers. It was bad enough coming to work every day and dealing with the staff- I was the lone English speaker in a kitchen filled with people that spoke mostly Spanish. It was me and a bunch of sassy, fiery Latinas from various countries... I wasn't so great at taking a ribbing at the time, so I quickly became the butt of the jokes. What "cured" me of my social anxiety was actually getting thrown on the drive-thru window... dealing with thousands of mouth breathing customers for 30-60 seconds at a time was almost like going speed dating for experience. I had to come out of my shell quickly and learn to talk to people. Eventually, I started joking with them, learning what one-liners didn't work, learning how I could make somebody laugh quickly. I dealt with more than my fair share of unhappy, complaining customers, and I quickly learned how to deal with a variety of people this way.
I guess my point is that you'll never get used to being social and being in the workplace until you've slogged your way through it for a few weeks. People can be cruel, horrible, and unhelpful to a socially awkward person, but you can only gain experience from dealing with it.
Edit: I call them mouth breathers because of the way they stare up at the menu when they can't decide which of the four choices to take. Blank, empty eyes, mouth agape... it's very flattering.
