Large flat roads are also more efficient. Have you ever driven down a bumpy road? That shit aint efficient. All of your horizontal speed gets turned into vertical speed in a jarringly unpleasant way. That’s part of why trains are so efficient because their tracks are so smooth.

Large wheels have nothing to do with a vehicles ability to go off road/on bumpy roads, if anything they’re counter productive because you want large soft tires and small wheels for that scenario.