Usually you need to transform power anyways on a train, because * lights, plug sockets, etc. are all at normal household voltages * often trains will run on m

Usually you need to transform power anyways on a train, because * lights, plug sockets, etc. are all at normal household voltages * often trains will run on multiple voltages, so a transformer needs to be involved anyways * lower voltages let you have thinner insulation, so thinner wires let you save space for things that matter more like a bigger passenger cabin