The only reason I can think of is Ziggler not winning is Vince wants him to remain heel. When he picks up the win at Extreme Rules he will be booed because everyone wont understand how he pulled out the victory... WWE has a potential Shawn Michaels on their hands, if he can be booked to use the Zig Zag and win match after match, the guy could be huge.
I know he has the WHC, but just like Bryan, imagine if he was actually pushed, instead of being over despite the shitty booking.
Crowd doesn't work like that anymore, they're going to cheer Ziggler winning at ER, not boo him. The whole "booking him as weak" thing doesn't work on smark crowds, which PPVs in the midwest tend towards.
Bryan not getting pushed is the finest example of Vince not actually caring about crowd reactions at all. Even more than the endless ignoring of Cena's bad reactions. Bryan routinely gets among the top 3 best overall crowd reactions (as in children AND adults of both gender cheering) at every show he's at, in any kind of smark crowd he's the most over guy of the night. He's more over than various other guys that get pushed heavily, like Ryback, or Del Rio, or Miz, or Sheamus, but he is still never used in a major capacity himself, he's never on the recieving end of a push, he's always used to try to get other guys over.
ANYONE with logic and business sense would give Bryan a big push as the crowd clearly are clambering for it, instead of "let's only push my hand-picked guy that I want to see, even if the crowd don't care much".
I watched that other night and all them never went together he never said that Daniel Bryan was better than him.
You need to understand that a major part of Punk's motivation is believing in himself completely, meaning that he has to believe he's really the best in the world, even if Bryan IS better than him, he's going to keep on believing he's the best because it provides him with a real drive and ambition. If he feels someone is better than him, then he isn't doing his best to BE the best.