They stare at a door because either
- it's slam door and they expect it to open automatically
- it's a sliding door and they expect it to open automatically
Ah yes, reminds me of an occasion down on the South Coast during the final years of the slammers. We departed Eastbourne and upon arrival at Polegate this young lad, probably one of the foreign language students who populate the area during summer, walked into the end vestibule to alight. Sitting in the end bay, opposite, I could see what was happening - he was quite clearly looking around for the button to open the door. So I leapt to his aid.
I can't remember whether it was the driver's bell or the guard's switch I could hear, but the sequence went something like:
'ding ding' as I opened the door,
hiss of brakes being released as he jumped out,
'ding' as I closed the door
and finally 'ding ding' again.
The delay was minimal but I must have caused an annoyance!