Re: No they don't
"The reason we use AC rather than DC is because it's more efficient to transport over long distance, lossy power lines, and more efficient to step up and down in voltage"
ITYM: It's more efficient to use High Voltage to transport over long distance.
HV AC lines have non-insignificant losses when transported over long distances.
DC is better - the higher the frequency, the higher the losses, but the less iron needed in transformers - which is why aircraft systems are 400Hz and older HV electric train systems used 16Hz (AC has one major advantage over DC - any arcs which might be generated self-extinguish every half cycle)
What is true is that it USED to be more efficient to step up/down using AC, but that hasn't been true for over a decade, and that's been leading to quiet changes in power distribution infrastructure worldwide.
+1 for standardised DC supply voltages, but it has to be borne in mind that DC distribution setups have to be built to deal with and control arcs (this is why switches are usually rated for 20% of the DC current vs their AC rating.).
240V DC distribution used to be common in many industrial areas. It was discontinued because it's unsafe - one anecdote I've heard related was that a blown bulb arced internally, and the arc then ate its way through the bulb base, socket, suspending wire and into the ceiling rose before someone managed to shut the power off.
Personal experience from cutting through a live 48V feed (4mm2 wiring) is that the amount of current which flows is scary (the wiring got hot before the fuse at the other end blew and the arc completely destroyed the wirecutters I was using - the feed was supposed to be dead.). On another occasion I watched a 22mm spanner accidentally dropped between 48V busbars get completely destroyed and the resulting arc almost became self-sustaining.
Lower voltages may be less inclined to arc, but they need higher currents, which in turn means heavier cabling. It's all roundabouts and swings.
+1 also for 48V battery, but higher voltages are better in your storage bank because that translates to lower charge/discharge current (longer life, less droop) and thinner wiring (less voltage drop, lower cost). Electric cars often use 600V - 48V is used in telcos because that's about the highest voltage which is "safe" for dry skin to come in contact with. and using heavier wiring isn't a major problem. Higher voltages are regarded as "mains" for all intents and purposes and usually require electrical qualifications to work on and sign off on.)