The ace product manager wonks over in Amsterdam never disclose their reasoning to us. Probably just as well -- it avoids becoming fodder for our amusement.
Truth to tell, their Live subscription servers have enough problems, and perhaps limiting transactions to 1/12 the previous volume helps to prevent them from going catatonic? At a minimum, it's 1/12 of the number of transactions to go wrong and have to deal with by phone after the fact.