Because in the long run I see Dybala having the role similar to Messi. I don't think it will work well with another left sided AMC and a 3-1-2 system. Right now we can see the Dybala - Pogba partnership and imho pogba goes way too much to the left to fit the team play, but he is sacrificing himself there.
What I want is another (ISCO; NEDVED; ADP) mobile, right-footed, technical player like Dybala opening up things from the LEFT. The way Neymar does it for Barcelona, albeit with a lot less speed - as our playstyle is a tad different. That way Pogba is allowed to roam more and ideally go for crosses in the area.
My avatar shows what I would love, but its unrealistic and frankly not that much of a value proposition these days.