Why? He's crap!!! A one day sunday bully!
Yes because only crap players can deal with the pressure of captaincy and average 50 this season on difficult pitches.. I don't think he is quite ready to go into the England team, however if he continues to perform well then I see no reason why he can't move into the England team when the likes of Strauss and KP retire.
I'm not sure on James Taylor, his knock today was his first decent score of the season with an average of around 30, that's the not the form of an England batsman..
At the moment I'm favouring Bairstow because he has a good average so far this year, he's young(22) and he already has some international experience from his time playing in the ODI's and T20's.