The wires would be too big. You just can't send enough power at a low voltage. You'd need either lots of dedicated wires to each outlet, or a wire as big as a hose.
AC is nice because it's easy to convert to other voltages. With DC you'd need either the exact voltage - or a converter, and if you have a converter you might as well just go directly from AC.
Seems like Power over Ethernet would be a pretty good standard to go with. Right now it's good for 25.5 watts at 44 volts. Wikipedia says some vendors have tweaked the standard to use more lines and get it up to 51 watts. To over-simplify, the higher the voltage the less loss there is on the wire for a given amount of energy (amps).
Added bonus you get ethernet too so any devices like LED lights, cameras, etc can be programmable without wifi/zigbee/etc.
You would still need a DC/DC converter, and if you do that you might as well just go from AC.
You are thinking wall-wart type applications. I'm more along the lines of infrastructure, lights and other permanently installed devices that can be designed from the ground-up to operate at 44v.
AC is nice because it's easy to convert to other voltages. With DC you'd need either the exact voltage - or a converter, and if you have a converter you might as well just go directly from AC.