Even one of these, "he dropped it to the Rock" - right there. That's a huge thing. A huge opportunity to make money. It did ok. People instead WANTED to see Rock vs Cena. Look, I know this is the opposite of what the internet likes to hear, but goddamn, Punk was given more than anyone else and it just isn't enough. A match with Taker. Dropping the belt to the Rock. Heyman. A hell of a championship streak.
What else could they give him to make him in the same league as what Cena does? More merch? A different placement for his not-bad matches? Nothing could overcome (har) Cena's LEGIT legacy. It's so big that nobody's going to surpass it - it just has to go away in total and everyones' expectations will come back to earth on what's successful.
Long story short, Punk's reign was great. He did a bunch of great things. But when you insist on comparing him to Cena, he will always, ALWAYS fall short.
Totally feel you're mixed up with the reality of it. Cena's as non-offensive and perfect an icon (yes, icon..sigh) that WWE can have represent their brand. Punk's got a narrower audience, they all just won't shut up about it.