I'm not totally sure I understand your question, but I'll take a stab at it. I think the reason you don't see many households baptised anymore, is because its a one-time deal. Once a household is baptised then the only subsequent baptisms in that household would be for the children, individually, as they come into the family. The only time a household could be baptised today is when everyone (adults and children) in the family is unbaptised and the parents both want to receive baptism (for themselves and for their children.) I think this is pretty rare, even today, in the West.