Why do airliners have to park so accurately? I was watching some airport documentary and I noticed that the planes always had to park precisely. I honestly didn't think so much of it before, but in the documentary, an aircraft parked badly because the VDGS couldn't detect it correctly due to fog, so it had to be pushed back to park again with the help of a marshaller. 

The only two reasons for this I could come up with are the following:


Jetways: I figured it's because of the jetways, but they can move about so as to adapt to where the plane is. Plus, when parking on stands, the accuracy is the same and there is no jetway.
Aesthetics:  I also thought it could be about aesthetics, but the systems used to help the pilot park (a marshaller or VDGS) can be expensive so business-wise, it wouldn't make sense to be so strict on parking if it's just for the looks.
This is to ensure that there is space for all equipment around the aircraft. It's not critical to the centimeter, but if it's off by a meter or more there may be problems. For example, the tail may stick out into the taxiway behind or the nose may stick into the service road in front of the aircraft. While most aircraft stop with the nose wheel on or very near the stop-mark, the main wheels can be off by a few feet, depending on how early/late the pilot turns into the stand. 

Modern aerobridges have a wide range of movement to cater to various aircraft types, but nowadays there is a lot of equipment buried in the ground. You might see ground power and air conditioning hoses which plug into the ground next to the aircraft nosewheel area. If the aircraft is off by a few feet the hose/wires may cause obstruction to the ground crew. The hydrants for fuel also need to be near the fuelling ports - too far and the hoses might not reach.