Here in America, we pretty much bastardize any foreign holiday and make it our own by turning it into a drunken fest. Think about it: Cinco De Mayo? It's a Mexican holiday and we get drunk while wearing sombreros. St. Patrick's Day? Even if you aren't Irish, you drink like you are on that day.
Well because of this, folks that are of Irish decent feel pressured to celebrate the holiday even if they don't want to.