Because they want you to get off the stage.
Crowds may say "boo" as a way to express disapproval or disappointment. It is a vocal expression of their displeasure towards a performance, decision, or action.
cheer
if it was in wales most of the people in the crowd would be welsh so they would go for their team and boo their opponents
In Hawaiian, "boo boo" could be translated as "hau'oli" which means "sore" or "injured."
boo
Boo!
"Tengo un boo-boo." or "Tengo un dolor."
Peek a boo
"No me ignores boo"
they normally say how yummy bananas are.☺
Scout picks out Boo Radley from the crowd at the end of "To Kill a Mockingbird," realizing that he is the kind, mysterious neighbor who has been looking out for her and her family all along.
because 'boo' is something u say when u jump out to scare somone
It is easier for children to say