Some people will just stand in the way right after the doorway because they "don't want to stand up when the person for the window seat comes". There'll be others who spend an eternity getting their luggage into the overhead bin. And others will just put their luggage in the first overhead bin they see because "there might not be enough space where I'm sitting". The majority though will decide to derobe right at their seat for 5 minutes because they didn't have enough time to do so while waiting 2 hours before boarding.