240 V sockets are so 20th century!
Because you don't want to power a piddling 600W gaming PC or a 50" TV, or even just more than a few LED lights off a 12V bus. Just from the power draw alone that PC would be pulling 50 amps and require 6mm^2 wire cores, and it would still require stepping down to the 5V, 3.3V and lower voltages it uses internally. Running 12V and 5V buses in addition to the 230/240V AC takes a lot of extra cabling for not much gain; better to fit appropriate low-voltage sockets (USB, and something else for 12V) with the power supplies built in next to your standard AC mains sockets.
48V might look to be a better choice, but still requires step-down converters for just about anything. And solar panel output isn't some standard voltage anyway; for maximum efficiency there will be a MPPT fitted to each string, which already does quite a bit of voltage (and current) conversion again. There would also need to be a hefty central power supply for keeping stuff on at night and on overcast days, though creating an UPS would be somewhat easier because you can more or less just splice in a stack of batteries.
And there's the bit that any DC power distribution at voltages higher than 42V requires specific safety measures.
Biting the hand that feeds IT
