Why do people drink a lot on St. Patrick's Day?

It is based on the racial stereotype of the Irish as hard drinkers. As Saint Patrick is the patron saint of Ireland, drinking a lot is a way of identifying with the Irish. Of course, St Paddy's Day is really just an excuse to celebrate after a long cold winter and a break from the abstinence from liquor that many Irish Catholics undertake for Lent, which also occurs at this time of the year.

Because green tastes like beer.

I dont I dont drink at all

It's a traditional thing. People want to have fun and drink green beer. Why are there fireworks on the 4th of July?

St. Patrick's day is a day in honor of St. Patrick's death, the Patron St. of Ireland. Traditionally, the Irish feast and drink in honor for the deceased at a wake. So over the years as the holiday has become more Americanized, it has grown from a feast and some drinking, to a day known only for drinking. Not necessarily from the racial stereotype that the Irish love to drink. Although, that would be the easy assumption.

Do you have Irish in you??

It's because drinking on Lent (which st, patrick's day fall during) is not allowed expect on that day because traditionally during Irish wakes there is drinking and St. Patrick's day honor st. Patrick's death.

You can read the full story here:
http://www.associatedcontent.com/article/6156262/why_do_people_drink_on_saint_patricks.html?cat=74