It is time to replace my house batteries. I currently have two 12 volt deep cycle batteries tied together. But I have a question. Every houseboat I am familiar with uses 6 volt deep cycle batteries tied together for their inverter power and 12 volt deep cycle batteries tied together for the "house batteries". Everything I read says 6 volt are better for long term extended drain use...

So my question is; why doesn't anybody use 6 volt batteries as the basis of their house power?