The first person on, and the last person on - we all get there the same time !
You have an allocated seat !
A plane never, not takes off because of crowded overhead cabin storage.
If your first on, you still have to wait till the last one is on - do you enjoy sitting in a cramped airplane? Are you a voyeur wanting to gawk at incoming passengers?
Do you have a fear of empty spaces that you need to be enclosed as soon as possible within an aircraft?
Do you really think your priority boarding lane gets you a better service or makes you more important? (unless traveling Business/first class)
<side note> Why do people insist on jumping up when the seat belt sign is turned off when you arrive, especially on short haul flights??? I'll still see you at baggage claim !