Why do we have jack o lanterns
The original theory is that Jack o' lanterns kept spirits and monsters away. Whether you believe it or not it doesn't really matter. Right now it's so trick-or-treaters can know which houses have candy.
i don't know... becuase it's kinda scary?
Because bob-o-lanterns made no sense!
In Britain they carve ruttabaga not pumpkin. I saw this myself.