Call the fashion police!

Now there's nothing wrong with taking pride in your country, & one of those who celebrate the most is the Irish on St. Patrick's Day, which is actually in two days time, but London celebrate it (for cynical tourist purposes naturally!) on the nearest weekend at Trafalgar Square. Which happened to be this afternoon, so I passed through taking a few snaps. I didn't stay long, as the abundance & smell of alcohol was almost overpowering, & a bit un-nerving, for a recovering alcoholic like myself.
Can someone explain what it is with the Irish-both real & plastic-that makes them dress up like idiots once a year?