For many students needing financial aid, they need to compare offers, since they could make “barely affordable” work but would strongly prefer “easily affordable”, so that any sort of binding ED, or high school policy that forces them to treat EA as binding ED, would prevent them from applying early.
There are also non-super-selective schools which offer EA that is not rolling.
Would you object if a student used a school like UMass - Amherst as a probable safety and applied EA there, while also applying to other schools higher on his/her desirability list even if s/he got admitted to UMass - Amherst during the EA round? Would you force such a student to treat UMass - Amherst as ED in this case?