because it's the beginning point of the story

like ravenswood is pilot of pretty little liars

http://stream-tv.me/?s=pretty+little+lia...

I thinks its because its the very 1st episode that's sets off the show

Kind of like how a pilot sets off the plane

You cant have a plane without a pilot

Kinda like you can't have a show without the 1st episode

pilot light

because it takes off - like a plane? haha I dont know