Why do Adcoms hold decisions?

There are four reasons I can think of as to why they do this:

1. What do they have to gain by giving out admissions early?
There is no benefit, and there is a chance that they will change their mind. And as more people apply, the more information they will have available.

2. For the sake of the applicants
It is a painful process to wait and hear back. We all know this, and this is probably the reason why you are asking the question. But at the same time, once the admissions committee starts releasing decisions it becomes increasingly painful for the applicants. If they started rolling out admits people would be checking their email and phone every 5 seconds hoping that next email is an admit. If you know they won't post anything until a day or two before the deadline, the wait isn't so agonizing.

There is also another reason to this respect. If they started rolling out admits, you would know that the first people to get the admits would have been the "no questions asked, admit". And the closer it got to the deadline, the more you would know you were on the edge. It would feel like you were the last one picked by the captains at the kickball game. No fun. Or imagine if you were the first to recieve a ding. You'd be the "you suck, ding" applicant. NOOO THANKS.

3. Efficiency
Business school admissions processes are probably one of the most efficient processes around. I mean, you can't work at the business school without all that learning rubbing off. It's most efficient as a team to work through the process, then release all admits, then field questions, then help waitlisters, then start the process over... or something to that effect. This is one of the main reasons why so many schools have turned away from rolling admissions. It just makes more sense to find a process, and repeat it over and over, to maximize efficiency. With more applicants in this down economy, this make more sense then ever.

4. The harder you work to get in, the more you want to be a part of it:
Think of the fraternity brother who gets hazed during rush. This is the worst few months of his life, but when he's done, he feels like part of the group and has created a bond with his fellow members. This is kind of the same with a Bschool. It has been scientifically proven that the harder you work towards something, the more you feel a part of it, and a better sense of achievement you recieve if you accomplish it. So the harder they make you sweat it out, the more you want to be a part of it. It also gives them some leverage. I've heard of some applicants being weary of a bschool where they gained acceptance too easily. For example, if you applied and they accepted you 2 days later, you might think "hey, they really like me, I bet I can do beter!". In some ways its a negotiation tactic. Think of the guy that is waiting for a job offer, and they really make him sweat it out for months. By the time he gets the offer, he is not going to negotiate the salary, he just wants sign the dotted line.

Anyone else with any other ideas?