I'd imagine DC-DC conversion to be a bigger pain. Inc comparison is AC-AC is very easy, while you can use switched supplies and what not it can be noisy in an EMF/RF context. And low voltage DC (even something as "high" as 24V) can have massive sag/voltage drop off over 10-20m of wiring, similar to what the other commenter mentioned.
(Technically I'm sure using for eg motors, DC-DC could be done with minimal EMF noise, but you might end up with audible noise and efficiency losses.)
Unless you’re using a transformer, AC adds a complication: energy storage. A device that takes AC in, wants to have a high power factor draw’s power that’s proportional to V^2, so the power is a sine wave at twice the input frequency. Most loads want power that doesn’t have 100% ripple at 120 Hz, so the power supply somehow needs to store about a half-cycle worth of power to out the ripples. As a practical matter, you end up with two-stage power conversion, where the first stage is a “power factor corrected” conversion to a high intermediate voltage and the second stage converts to the final voltage.
Similarly, for AC output, you want that 100% ripple on the output but not on the input.
Three-phase AC avoids this particular problem — power factor 1.0 with >= 3 passes has constant total power. But even a three-phase-AC motor drive producing variable frequency three-phase output has an internal DC bus.
As a practical matter, IMO all large residential loads except resistive heating either should be, or already are, either DC or variable frequency drives.
(Technically I'm sure using for eg motors, DC-DC could be done with minimal EMF noise, but you might end up with audible noise and efficiency losses.)