A heel turn is always a good way to refresh the careers of guys that get stale as faces. When the crowd starts to reject a babyface, it is time for a heel turn. A lot of big stars, like The Rock, Stone Cold Steve Austin, and even Hulk Hogan turned heel eventually. But, that has never happened with John Cena.
If he got mostly negative reactions, the company would have turned him a long time ago. But, he gets cheered as much as he gets booed. Cena still has a huge fanbase, his merch is always selling good, he is a spokesman for the company and does a lot of charity work on behalf of the WWE. That is why Vince never made a move and switched Cena to the dark side.
Former WWE writer Kevin Eck talked wth PWTorch.com and said that John Cena almost made a heel turn back in 2012.
“We were very close. We had Vince sign off on it at one point and Cena was on board to do it. We started making plans for it and then Vince got cold feet – we had just signed an exclusive Cena merchandise deal with Walmart. Vince not only considered it, he was almost there to pull the trigger on it.”
He also noted that he couldn’t replace Cena as Vince McMahon felt that even though CM Punk is over as a face, he couldn’t be THE guy for the company while he knew that it couldn’t be Randy Orton as “he hates people.”