[arcticbull]

Correct me if I'm wrong but isn't the whole point of using AC that it's easy to convert voltages super-efficiently with transformers?

Having DC power at home seems like the worst of both worlds. Low voltage DC at home causes large losses in the wiring, and high voltage DC causes large losses in the step-down regulator (leaving you with a buck-type regulator operating at the low extreme of its duty cycle). After all, DC-DC conversion relies broadly on turning the DC into something vaguely sinusoidal and using an inductor - so its basically DC-AC-DC anyways.

Am I missing something?

[analog31]

Switchmode power supplies already tend to rectify and filter the high voltage AC before stepping it down. At high frequency, the transformer can be a lot smaller.

[dreamcompiler]

Not sinusoidal: Boost and buck converters use PWM square waves. Because the power transistors are almost always fully on or fully off the I2R losses in the transistors are quite low.