Could it be that the aircraft isnt actually ready to receive passengers??
Around here, crew check-in 1.5 hours prior to a flight, they brief and then get to the aircraft about an hour prior to departure. From that point on they have to load catering, conduct security checks and conduct equipment checks. When all of that is finished, they will accept passengers.
From a passengers point of view, i have sat in the back of a delayed B747 where the cabin temperature was over 60°C, passengers were threatening to smash the windows to get cool air! From that point on, I started to like the idea of boarding at the last minute!
Mutt.