There are massively diminishing returns. 1kW at 12V is 83A, which needs a rather beefy wire that is expensive to buy, annoying to route, difficult to route, and

There are massively diminishing returns. 1kW at 12V is 83A, which needs a rather beefy wire that is expensive to buy, annoying to route, difficult to route, and needs careful termination with large tools. 1kW at 48V is ~20A, which can be done with 12 gauge wire, which is not bad at all to work with.