Well, as I said technically that isn't true, you can get onboard earlier, you just can't get to your stateroom.
However, I really wonder about this trend of people wanting to get on the ship at the earliest possible moment. It seems everyone is going early now, which means lots of lines and waiting.
Is it really so fun to deal with the backup at security, and having to carry your bags all over the ship while you wait for your stateroom to open?
It used to be that if you got there early at least you avoided the later rush at 12:30 - 1:30. Now people want to arrive at 11:00 and wait for the ship to let them on. Why?
It took us a good hour to get onboard Mariner when we arrived at 11:30 am, where I have gotten to other ships where I checked in and was aboard within 10 minutes.