This has been already discussed and, of course, it's made for obvious performance reasons.
All jetways you see are static, which means they are the fastest to draw, so your fps won't slow down to a crawl when an airport with many jetways will load. They are replaced by their dynamic version only after you activate your own gate, so the fps impact of just one dynamic jetway is minimal.
When they retract, they will go back being a static model.
Being static, means they only have ONE position, then one they have been modeled with and, of course, the modeled static position can only be straight, so the dynamic created from that position would be able to reach the widest range of doors.
That's also why we cannot have jetways placed at random/different positions too, which would surely looks nicer and more realistic, but it would require having a DIFFERENT static model for each gate which, in addition to make the number of static models installed in the sim to explode (slowing down the startup and increasing the memory required), would also affect fps, since even if they were all static, being *different* models would make them slower on fps.
The only way to achieve this would be simply forget the static models, and have them all dynamic at all times, so we could do random initial positions, random retract position, and of course, we would DESTROY the frame rate doing this.
Believe me, it took a lot of time/effort to alternate between static/dynamic to save your fps. It would be *much* easier to code for us, and better for eye-candy (screenshots), if we just forgot about optimizations and make them all dynamic.
