If they simply got rid of choreography, or combined it with interpretation, that would throw that particular balance off and perhaps put too much emphasis on technical skill (which already has half of the score all by itself in TES) at the expense of the "performing art" aspect.
Even if all skaters automatically got almost identical scores in the triumvirate of PE, IN and CH, this gives a way of tripling the weight of this part of the score, which might otherwise get lost altogether. (?)