My bicycle is significantly more efficient getting me to the train station than the bus is.
I walk because it costs 150 yen or so to park the bike. That's still more efficient. I don't live close to a bus stop. Lots of people near me don't live close to a bus stop.
More than half the people going into the station at any particular time of the morning have not come in on a bus. And most buses at this station are about half-full, not operating at maximum efficiency.
The plain and simple fact is that we are not all going from and to the same place at the same time. Buses and trains are very useful in certain traffic corridors, but rely on small-volume transport to fill in the very huge gaps.
That said, there is still more to say. If Intel threw as much money at ARM as they do at x86, ARM could be even that much more efficient at the smaller design rules Intel has to resort to to make x86 anywhere close to efficient. And if Intel had joined (for example) the PPC consortia with the engineers they head-hunted away from better designs, they could have much more efficient server CPUs than any x86 CPU they have now or ever will have.
But, if they had done so, they could not have maintained their practical monopoly on desktop processors, and they would have given up their strategic inroads on servers. (Because someone else owns the IP, you see.)