People forget that it is not just the processor that consumes power. The reason the new MacBooks are so efficient is not just because they are ARM-based, it is also because they have incredibly energy efficient screens, WiFi, RAM, SSDs, etc. They can achieve this through their sophisticated manufacturing process, with highly integrated components directly soldered onto the board, a fact that is widely (and correctly)…
Is it really that hard to design sockets that don't waste such a significant amount of energy? Honest question. Do you really save so much by soldering something without any type of ribbon, socket, or other removable connector in between?
I'd assume all the low-hanging fruit is _long_ gone there, though.