Outlets are cheap and easy to wire. Running low-voltage cable throughout your house to supply USB ports in outlet panels isn't - especially since, at least in the US, you can't run HV and LV cable in the same conduits and still pass inspection. (Nor should you! Suddenly having 120VAC@10A on a USB port's power pins is a Bad Thing.)
Yeah. I'd rather do the conversion once or twice - say, 2x high quality 5x USB ports from Anker or similar than to have it somewhere I need an electrician to modify.
