@OmSigDAVID,
I haven't researched the people who started it, but for long time, a lot of people have gone with it, what with the wearing of the green and booze.
If there is anything sometimes true about the irish or later american generations, it's that we hold, even savor, grudges. (Consider my angry aunt..)
It's only fair that grudges can have equal representation.
I don't mean to make light of real irish pride.