The 'why didn't the Incas, who were brilliant engineers eminently capable of mastering the axle, invent the wheel' is a fun question too. But one easily answered by looking at how little of their territory is flat enough for a wheel to be useful.
Plenty of people use cars, buses and railways in Peru today. The wheel is definitely useful in that territory, it just wasn't advantageous enough to over existing tech, so it needed to wait until complementary technologies had been invented in other cultures.
Made a lot more sense to start cutting and maintaining gently graded roads through the Andes for civilisations who started millennia earlier with the premise that horses/oxen were available and good at pulling stuff and once you got through the mountains everything would be nice and flat. Iron helped a lot too, of course.
The wheel still isn't particularly useful in reaching a number of Inca sites even given dynamite and the internal combustion engine. It wasn't that Incas were averse to the concept of roads so much as they didn't see why roads shouldn't have stairs.
Llamas are good at climbing steps and terrible at pulling carts...
