What two reasons should you wear green on Saint Patrick's Day?

In America it is tradition for EVERYONE to wear something green. School kids have a tradition of their own, if you are caught without something green: you get a pinch. Not a mean pinch, it's all in fun. It is also considered good luck to wear green on St. Patrick's day. Wearing green also serves as making you Irish by proxy, if you are not actually Irish. America has a huge population of Irish descendants.