DC power has many problems as a household power distribution system, and there may be other answers to the wart problem. You need to consider the effects of wiring, efficiency, etc. There are good reasons why even remote PV powered residences use AC distribution within the home.

I was asked a similar question at a meeting about LED lighting. LED lights use 5V DC and are roughly the same efficiency as flourescents. So a normal bright room light needs 20W (it contains multiple LEDs). At 5V that is 4 amps.

Power loss due to resistance goes as I^2*R. For a 100ft run of 12 gauge copper (typical 20A rated home wiring) R is 0.3 ohms. If you operate at 5V that one light would consume an additional 5W (16*0.3) to heat the wires. If you move up to 10Amps (50W) you also consume a whopping 30W heating the wires. So DC wastes 20-50% of your power. That same 20W light on 200v AC has a wire loss of 0.003W, which is quite insignificant.

For more power hungry devices like PCs, microwaves, or air conditioners a 5V system would need 250amp service. That is utterly impractical. So you will also need 100V+ service in the house. Dual wiring is expensive so you need really compelling reasons to add DC.

AC has other advantages. It is easy to shift AC voltages with transformers. DC to DC voltage shifting is very hard for up, not so hard for down. Internally, CRTs and microwaves need 10-50KVolts. Other common needs are 40v, 10v, 5v, and 3v. It's easy to get all of these with transformers.

Similarly, variable frequency AC is superior for motors. DC is very simple, but unreliable and less efficient. Improvements in power semiconductors have made variable frequency AC motors affordable. They are much more reliable and efficient than DC motors. Railroad locomotives have largely shifted over to variable frequency AC and the proposal for next generation automobiles is variable frequency AC.

The automotive proposal is for the frequency to be up in the 5-20KHz range, and the voltage to be approximately 40V. That lets them replace hydraulics (brakes, steering) and mechanicals (air conditioner, valves) with electronic components. The variable frequency AC components are impractical without modern power semiconductors, but they are also more reliable and more efficient than the hydraulic and mechanical components that they replace. For the devices that need DC (radio, LED lights) the higher frequency AC lets the AC to DC converter be much simpler. It can be put onto a single hybrid chip and integrated into the LED socket or electronics card.

For the home market you have the problem that higher frequency AC has many problems for power distribution. The 50-60Hz AC is really very good for the metropolitan power distribution efficiency. The low frequency minimizes resonance losses to the earth.

The change that I see is different. Some of my newest equipment has AC to DC converters that are no larger than a typical 3-prong plug. They generate variable voltage DC (6-10v). It looks like a poorly filtered power supply, and is probably a diode bridge with modest filtering. That keeps the analog components small. Then there is a DC to DC down converter to 5V or 3V within the device. This kind of splits the power supply into an small AC cord part and a small device part. For power levels up to about 10W this size reduction seems feasible. Above that you need some breakthroughs in analog component sizes. If you pick just a few amperage ratings, e.g., 0.1A, 0.5A, 1.0A controlled off plug shape you end up with a simple DC powering environment where three common cords support any device that needs up to 10V and up to 10W. The device half deals with the particular device requirements.

The USB path is a dead end for higher power requirements. The tiny wires in the USB cable have a high resistance. They limit the USB power to under 0.5A for a reason. If you push it much further you end up with hot wires, significant voltage loss, or both.