How exactly has he been benched? He's played in 7 straight Serie A matches, started 3 of them, played at least 16 minutes (plus injury time) in the other 4. And also played the entire 2nd half against Ajax.
This is a just-turned 19 year old kid, in a team full of established, top players. He's been on a very good run, but there's no need to rush things with him right now... I'd like to see him play in each match, but it doesn't matter whether he starts or is subbed on with substantial time to show his stuff. I'm sure he will get another start or 2 in our last few matches, but there's no need to fret about it as long as he's seeing the pitch, and developing... and it seems Allegri and the club have done a pretty good job of it with him this far.