Why DID we lose our tails?

Bridgette from Girls Next Door (the slighyl chunkier, slightly stupider one) is the best! I just love when she asks why we lost our tails. It's a long movie, but just keep fast forewarding to her. We would be best friends if we hung out. Fave quote:

"The Captain Morgan really looked like Captain Morgan. Not like, Jonny Depp or anything"