240VDC is way too dangerous for residential use. And really it's not super practical to drop that down to 5v for charging your widgets. 48V makes much more sense.

And for that matter, I wouldn't want 240VDC on utility poles either. If a line goes down, it's so much more dangerous.

The more sane solution would be a high capacity DC converter installed next to the line transformer that feeds your street. DC infrastructure inside the home makes total sense at moderate voltages. City scale DC at line voltages is honestly terrifying.