I stated it on another CC thread before but I’ll rephrase it here:
Unrestricted EA gives an applicant a valuable option. Just like a stock option, the holder of the option (in this case, the applicant) has a right but not the ***obligation *** to choose something. The cost of the option is borne by the school (the writer of the option). SCEA restricts that option (i.e. puts conditions on the exercise of the option), making the option less valuable to the applicant, and therefore less costly to the school. ED completely takes away that option, making it worthless, entirely eliminating that cost to the school. This is just simple math and economics. And it is this simple economics that drives what the schools are doing.