GAN is not just faster and smaller, it's side effect is also efficiency.
But it's currently still a high end way of going power switching. So it's more expensive, so not all power supplies use it yet
House power wise our biggest users are AC appliances (heat pumps) they do not benefit from a more efficient DC adapter.
A phone at 5000mah who charges every day from 0-100% would use 5Ax4.2Vx365d = 7,665 Kwh x โฌ0,22 = โฌ1,68 (excluding efficiency loses). This is too small to make reasable investments in phone adapters. But I do see that a better computer power supply (when use regularly) can make a difference to your power bill