Maintenance on most large farm equipment is performed from the side. In a pinch, the undercarriage is also usually several feet off the ground at rest because it needs significantly more ground clearance than a road vehicle.

As for changing tires and such, actually you do floor jack up a combine. It’s just a really beefy hydraulic jack.

A very small area for that and there would need to be an entrance or exit. The stairs look like they are in the way.