C'mon, testing your willpower is a challenge! Don't you like challenge? Isn't that what this is all about?
Well if the AI isn't a challenge, then it means you're probably beating them by a fair margin. At which point there's not a lot of tension in the first place because you can make little mistakes here and there, not go as fast as you can, and still win. If we're trying to take the psychological aspects of this into account, then that's how it works. The only thing that taking away rewind does in those cases is........well, nothing. Its not affecting you, is it? There's not even any niggling itch to use rewind because you're already beating the AI easily anyways.
I still think you should get into online racing more man, since you enjoy challenge and the 'sim' side of these games. There's no rewind, there's top flight opponents and you will get much better, much quicker. No offense to anyone here who this applies to, but, I see people spend hundreds of hours 100%'ing the career events and whatnot and yet they aren't even all that quick. If that time had been spent racing online or improving their skills with Rivals or hotlapping against high level ghosts, they would be so much better. There's nothing wrong with spending your time in career mode if that's what you enjoy, just saying, I don't think the track is challenging you nearly as much as you think it is when you have AI as your competition. When you *need* to get quicker to beat faster opponents, you will have to find new lines and learn to be more and more consistent and perfect. Psychologically, racing against AI severely limits the amount the track is actually challenging you.
For what its worth!