Why does Split Second's ending have a semblance of plot?

I was playing Split Second the other day, and after completing the final elite race in Season Mode, I was surprised to see the game attempt some sort of story, and of course it was a twist cliff-hanger ending. 
 
Now, I don't really mind twist/cliffhanger endings, but why have the end of the game be the only bit with story? Up to that point, the only "story" was the premise for the game (it's a TV show). Why even bother throwing plot in it? Clearly if people played to the end they didn't need to be motivated by story to do so (the game is quite fun).  
 
Well, I guess that if they're going to be changing something in the eventual sequel, it does help to explain why, but why not just explain it in the sequel? Or perhaps have there be bits of plot throughout the whole game? Why not hint at what happens at the end throughout the game instead of simply throwing it in at the last minute?