Why is pie one of the most used thing when people are asked to be random?

Actually, it's quite simple.
It has nothing to do with "pie", but instead, it has to do with "Pi".
As "pi" is very look alike, phonetically, with "pie" and it's a very aleatório number (the numbers don't go por a certain order or rule), people associated "pie" with random.

Because people are weird. Honestly, Idont think pie is that good. Please dont be mad at me for saying that pie lovers

This is exactly why I said that pie doesn't seem that aleatório anymore. It's expected. I honestly don't know. I like pie, but why? Hey, that rhymes :')

But I don't know. I guess it's just one of those things that catches on. :P

pie is awesome. i can throw a pie at ur face, pie myself, or throw it at a computer when i get frustrated with it, pie wins

Pie.