World's oldest wheel - photo

[NortonDommi]

Having the whole axle turn means that easily made and replaceable bearing/s could be used and they could be made long enough to spread load and reduce wear also provide positive axle location.

Ralph, if you ever see a skilled woodworker cut a timber to shape with an axe you will be amazed at just how fast and accurate they can be. Think of wheelwrights, shipwrights, millwrights etc. A lot of round timber is used in holes tight and loose.