In a perfect world we'd have both AC & DC, and could use whichever was most appropriate. We could feed DC straight from the solar panels to the cell phone. But in terms of what consumes most of the power, in the typical home it's AC loads.
This isn't an appropriate comparison. Those appliances actually do useful things that need to get done so the energy isn't just wasted like it is with power supply inefficiency.
Sure a 12vdc circuit would be nice. It wouldn't be nice enough or efficient enough to be worth paying for.
I hate waste; my mains-connected smoke detectors (1% efficient) and garage door opener (15W standby) gnaw at my soul. But that's scope for improvement, not an efficiency crisis.
Those aren’t a waste, they are critical life safety equipment. If their 1% efficient power supply lasts the full 10 year lifespan of a smoke detector rather than 6-18 months like a typical LED lightbulb, I’d say that’s the appropriate level of reliability.
If every home in Australia had two smoke alarms, that means 5,600 kW of continuous and largely wasted energy consumption. I don't mean wasted in purpose: smoke alarms are essential. The wasteful part is the fact that 99% of the power going into smoke alarms goes to converting AC power to DC power.
As far as I'm concerned, that's 99% scope for improvement.
https://reductionrevolution.com.au/blogs/news-reviews/584256...
Although 15W standby for a garage opener seems excessive.