I think one of the reasons there were so many EA deferrals last year (and will be this year as well) is financial aid. First deferrals take the pressure off the financial office getting the packages completed before Dec 17. It also gives the financial aid team the opportunity to see what the RD pool looks like before commiting merit funds.
They are not likely to lose too many students because of the deferral since no one is deciding before May 1 anyway. There may be initial disappointment but that will be erased by an acceptance in the spring.