Why can't I get into racing sims?

[ps3-sales!]

I really don't like racing sims. I don't know why, I just find them very boring and only catering to people who have a fetish for cars and the parts that go on cars, and not the gamer. 

I'm a big racing fan however. Burnout paradise, Need for speed most wanted (2005, recently bought 2012 however), the motorstorm franchise, and pretty much every Mario Kart game would be my games of choice for the genre. I put a lot of hours into my racing games over the years. 

As far the sims go, I've tried to put an effort forth to enjoying them. With all the sales the series has gotten, I figured Gran turismo would be a good starting place. I borrowed from a friend and played for a day before giving it back. Honestly it wasn't even remotly fun. It felt like a chore to win races. 

Same thing for Forza, to a lesser extent. I feel Microsoft has tried to make the Forza series a bit more accesible to the casual racing fans, but in the end the gameplay just doesn't do it for me.

Am I not understanding how to play racing sims?