Shyness is not a trait born with. It's developmental.
If people share my experience, then shy people just need a better excuse to do stuff other people do. I do not classify myself as shy, though I do have lots of shy moments. It mainly depends on my mood. But then again, I'm not your average one personality person. But that's not the theme of my theory right now. To clarify, let me consider my shy moments as basis for my theory.
We shy people care too much. About what other people may think, about common sense which is nothing more than society standards, which by the way varies quite a lot, about the consequences of our acts, among other concerns. When given the right answers to those concerns, shy people do what other let's say non-shy people do.
There was someone who said that humans are social animals. We live in community and we tend to reach out for others. So, it's our nature to establish relationships.
Shy people have friends too, they may have fewer friends, maybe closer friends, but they do have friends.
Shy people talk to strangers, when they have a good reason, an imperative reason to do so, just like normal people can ask a stranger what time it is.
Shy people dance and sing. They may not usually do it in public, but given strong reasons, they can do so. They may develop stage fright which can be quite limiting, sometimes it requires some treatment, but sometimes one overcomes it.
Shy people don't want to disappoint the audience by singing lousily and dancing crappily. They care what the audience thinks. Some people just don't care.
Shy people don't talk to strangers because they are concerned with the consequences of dealing in an unknown environment. Some people just don't care. What can possibly happen?
Shy people don't participate in class because they are afraid to have to wrong answer. And then, teacher might think they are stupid and students might think they are stupid. Or they could get the right answer, which makes the teacher happy, maybe the students too, but there is also a case when others think that they are so geek and smartass. It's a double edged sword. In the lack of a better argument, shy people just don't speak up in class.
Now, people are not born with fright of the unknown. We learn that with society, in class and from our family. Depending on the values other people pass to us, and what we take from our environment, shyness may develop. I can recall perfectly. I was not a shy person until probably middle school. That's when all the discrimination and peer pressure began. Society almost forces shyness into a person. I won't say it's society's fault. It's not Some people are more susceptible, some people are more prone to weight the pros and cons. Me, I changed my attitude.
Evolve and adapt, from then on, I got a brand new shy adjective to describe myself. Am I any different from other people? Not really. I just need a way better reason to drink myself till drunk and do some incredibly embarrassing things. I just need a better excuse to do certain public things.