I don't know about others-----
I have 24vdc on my power boat
. I also have a huge, old 12vdc house bank that I will replace this spring with 4 each 6vdc batteries. I also have a separate battery for my generator
Back to the 24 volt bank......... its purpose is two fold. First I dread the thought of having my Maxwell
run a battery down when the windlass must be functional. Also because the windlass has a large current
draw I wanted to avoid the voltage drop in the wiring to the windlass.
I also use the 24vdc bank to operate a 1500 watt inverter
that provides power to our TV, laptop
& microwave. We can watch TV all day & night without noticeably discharging that bank. As a point of interest, the higher your DC supply voltage is, the higher your conversion efficiency will be.
The house bank is used for starting AND to power a 1KW true sinewave inverter
for our 8.3cu ft fridge that has an interior
light AND IS SELF DEFROST.
My humble opinion is that boats, cars and trucks should be using much higher voltages because of the increase in efficiencies at higher voltages.