>>50743710Because they have to "make up" for Ash's prior league losses first.
Ash beat Iris which is close enough to beating the Unova League already, now he'll beat Steven to fully cement he can mog the Hoenn League after he made a joke out of Wallace, then he'll beat Cynthia to make up for Tobias.
Meanwhile Leon mogs Alain and Diantha, and by merit of Ash mogging Leon, he'll "make up" for his Kalos League Loss because he beat the guy who beat the guy who beat him AND Kalos' Champion.