People can have many reasons for being shy. Having problems, not being good around people, being shy around multiple people, being shy around women, family problems can cause shyness as well.
I personally don't like most people. Most people I know are incapable of holding up an intelligent conversation. And others are whores and point out any small mistake in your speech, even if they only misheard you. (I talk relatively fast and quiet, for the record.) Not to say I'm shy, I just stay away from people who are idiots and starfishs. Which is pretty much every teenager anywhere, probably including myself. However I cannot judge myself because I cannot see my actions from the outside... I also hate people who are hypocrites, which is, similar the last statement, pretty much every person everywhere.