Appearances can be deceiving. The view "behind" a Piper Cherokee looks something like the image below: no rear window so you can't see what's behind you, but that really doesn't matter since there's no way to go "backward" in this aircraft using the flight controls.
Visibility aside, ground handling is often a a complex production, particularly for larger aircraft or when you have a lot of aircraft in proximity to each other or obstacles.
Moving small aircraft around typically requires at least 3 people. When you're moving forward you will have the person operating the tug and two "wing walkers" who stand a few feet off the wingtips and walk along to make sure the wings aren't going to hit anything. When pushing an aircraft back in a tightly packed hangar there's sometimes a fourth person walking ahead of the tail to make sure you don't back the plane into something.
Since there's not usually much for the pilot to do inside the plane at this point, they usually serve as one of the walkers.
Larger aircraft observe similar procedures, but for push-backs or power-backs it's known that the area behind the aircraft is clear (this is usually coordinated over the radio), and as long as the tug driver or pilot keeps the nosewheel on the appropriate pavement markings there will be wingtip clearance.
Line personnel are also often stationed to guide aircraft to and from parking in close quarters where positioning is critical (e.g. when pulling an airliner up to a gate, or parking a small aircraft on a busy ramp).
The other half of the picture is taxiing under your own power and control.
When taxiing, it's generally assumed that the pilot knows their aircraft's dimensions and will avoid hitting things. This usually works out well, but that is not always the case.
Airport taxiways are marked so an aircraft with a specific maximum wingspan will be clear of any obstacles while taxiing along the centerline, and as you're generally only going forward that's where visibility is most important (you can assume if the area your wingtip was going to hit was clear 15 seconds ago when you last saw it and nothing was heading into that area it's still clear now, and you're relying on the pilot of the aircraft behind you to be paying attention and not taxi into your tail).