BECAUSE

 Mnemonic:
Big Elephants Can Always Understand Small Elephants

 Mnemonic:
Big Elephants Cause Accidents Under Small Elephants

 Mnemonic:
Big Elephants Can't Always Use Small Exits

 Mnemonic:
Big Elephants Can’t Always Use Small Entrances

 Mnemonic:
Because e Cannot Always (get) Under Smaller es