Maybe when people pay a lot for things on a date the other half will become used to having things bought for them and end up expecting it during the relationship. Then when the "payee" hasn't the cash, the relationship will begin to break up as the "non-payee" starts wondering why they aren't having things bought for them - "You don't love me any more!"

Just a horribly random guestimate there. Don't quote me on it.