I know it goes against the "policy" that gsx should be self-sufficient and require small inputs from the user, but calling the stairs as a first step in the preparation of the aircraft makes sense. Otherwise it's just weird to call for refuel/catering without stairs attached (I know they move in after we call catering
The policy is more like "GSX should not do anything automatically", in order to be less intrusive as possible when used with other software. For example, latest PMDG airplanes have their own service vehicles so, right now, you can choose which one to use, which would be difficult if GSX instead automatically did things on its own automatically.
And, it was originally made this way because, when GSX initially came out, it was a newcomer over an established product which was AES at the time, and that one DID started its services automatically when you parked the plane so, in order to let users more freedom of choice, we decided to NOT doing anything unless you call GSX explicitly, for example because you might have bought AES credits for an airport, and didn't want the two products doing the same thing, automatically. We were more or less promised that AES would be updated to stop doing things automatically as well with some configuration setting, but this never came.
Of course, flash forward 7 years, the situation is a bit different, and GSX is the clear market leader, considering AES basically died from the lack of updates to support the latest sims so, in theory, we might doing more assumptions about possible conflict with other similar software, and doing more stuff automatically, but I think in the long run it's always best trying to play nice with other products, and helping airplane developers interface with us in the proper way instead.