there is a few options
1. boarding taking too long
2. short of meals
3. not enough vegetarian meals
4. toilets not been empty
5. cleaners still on board
6. purser is late
7. captain got lost in the terminal
8. etc,etc,etc,etc,etc,etc
if i was you i wouldnt be to worry, at the end of the day you are not paying the parking fees!!!!!!!!!