There was once upon a time where that was true. The champion was the most important guy in the company. It's not like that anymore. Contrary to what a lot of people want to believe, it is all about who draws the most money. It's a business. The top priority of a business? To make money.
Lesnar, Rock, Cena, there's a reason why they're all featured more prominently than Punk, they bring in money. Not only that, they bring in fans from other dynamics, not just wrestling. You can't really say the same about Punk.
Sometimes thinking for the short term is better. Last year when CM Punk walked out with the WWE Championship, it would have been wise to keep him off TV for months, but the angle was so hot that they brought him back right away. Why? To sell Summerslam.
At the end of the day, that's what it's all about, making money. Not "people power" or respecting the titles. Vince McMahon wants more money in his pockets. And he knows that Lesnar vs Cena is going to make him more money than anything short of Rock vs Cena