There isn't the room. Sometimes they have to use the front door due to weather conditions at the back, but the problem is that the bus can't then move around, everyone has to stay clear of the wings, and so passengers still need to walk to the back of the aircraft.

I have had a few of these recently from domestics and trying to smother Zen like travel on to the cold fury is sometimes a stretch even for me.

The most recent situation was made much, much worse when there were two buses arranged. Full and standing, so I would guess 90% of legal capacity. The first bus left, but on it was a passenger who inadvertently picked up the bag of a passenger who was on bus 2. This is very easy to do when offloading from the rear, people's spatial layout gets all re-arranged and not in a good way. Bus 1 had arrived in Domestic arrivals when the bus2 passenger realised his bag had been picked up - had it been forward offload then he may have been able to intervene sooner. This then left the bus1 passenger's correct bag in the hands of bus2 passenger, who was then asked to leave it behind. He said something on the lines that he wanted to open the bag to find out the other passenger's details and arrange a swap, the IFL said "no, we will let the baggage team do that", but the passenger then had a argument with the IFL saying if he had no bag, he had no leverage (or words to that effect). Furthermore the IFL said they would have to transfer the bag to the baggage team, and that would take a while, and no they didn't have any contact details. So for those of us over in CE listening in on this, it did rather string out the process.

This was BA's standard approach in LGW, particularly domestic, until the new corridor for UK arrivals was opened (a few months before The Thing).