He doesn't like to play Ronaldo as the main striker. That's of course understandable because Ronaldo is used to playing with a clear striker that does the wrestling with the opposition CBs. Thus we've used Mandzo there. However we have played some of our best games this season with Dybala and Ronaldo playing up top (Bologna, United).
Saw Lucas Moura playing through the middle in the CL semi against Ajax? Dybala is slower but superior finisher. He could easily do that if Allegri trust him as striker.