Look at us, we're just Cruise question crazy!
Hmmm, I didn't even know there was staggered boarding! I have no idea WHY they do it but my guess would be to keep down the lines of people trying to board all at once or the check-in lines at the port down. Maybe they are just trying to keep it as chaos free as possibly. Heck, maybe they load the "adults only" parties on the boat first so you'll spend some money on tropical drinks.
