Reasons for not celebrating St Patrick's Day:

1. I don't wear green.
   
2. I'm not Irish, I'm Welsh (the bits of me that aren't Australian, that is).
   
3. I'm not Christian, and certainly not Catholic, so why should I celebrate one of their Saints?
   
4. What he did to get canonised was 'drive the snakes out of Ireland', which basically means he got rid of the native, Celtic-pagan religion. I don't stand for shenanigans like that.

Reasons for celebrating St Patrick's Day:

1. I like Guinness.

Plus someone posited the reason: "Because you can get pissed."

My response was: "I'm Australian; I can get pissed any day of the year."