Substitute V = A * R into W = V * A to get equivalently:
W = A^2 * R
or:
W = V / R^2
This is the power lost as heat in the wiring. You can see that losses increase with the square of current, but only linearly with voltage. Its about losses in long wiring runs at 48VDC. Compare typical household 10A at 240VAC with 50A at 48VDC for 1km of wiring in a data centre. 10A requires 14AWG wiring which is 8.450 ohm/km with conductor area of 2.08mm2. 50A requires 6AWG wire which is 1.320 ohm/km with conductor area of 13.30mm2.
10A Wiring Power Loss = 10^2 * 8.45 = 845W
50A Wiring Power Loss = 50^2 * 1.32 = 3300W
Ratio 3300/845 = 3.9
However, economic cost of install also needs to be considered. Ratio of conductor area:
13.3 / 2.08 = 6.4 times copper for 48VDC system, hence 6.4 times more expensive in materials to install.
Add to this the significant additional labour labour of working with larger, heavier and stiffer cable.