One of the perks of being an elite (even a lowly MVP) was pre boarding so you don't have to get stuck in the aisle while people are wandering around trying to find their rows and perhaps give you a moment or two to get settled before your seatmate shows up. While not every elite may want to take advantage of that perk I do.
It also seemed to me since the flight attendants don't know who is boarding and who isn't that they have no way to keep people who have boarded early saying they would not use the overhead from actually using the overhead.