Since patch 1.10 you can't do it on Like The Wind anymore. However, I think you can still do it on the Dream Car Championship. It just takes longer.
It's still quicker money to run the Ferrari Seasonal on Le Sarthe.
Nothing is quicker than setting up rubber bands, going to sleep, and waking up to several million dollars in your bank account. I want my seat time to be racing against real people, not robots, I did that for 10 years and it was old after GT1.
As to the rest of it, we all have lives, I even have one, and I rubber banded after I got to level 35 and my garage is awesome. People forget this is just a game, it's not real, there's no
"cheating" only what the game allows you to do. If Kaz wanted to stop the rubber band grinding they could easily do a special mod on the X2010 so it slows another 50 km/h on Dream Car and voila, no more rubber band grinding. This isn't 1987, and they have an army of programmers available to do this stuff, he isn't working out of his garage. They did it for Like the Wind...lol...but not for Dream Car..anyone wonder why?
Me personally I find the Seasonal's incredibly tedious. After you've raced online, wheel to wheel at the limits of your car, against equally talented drivers, the seasonals and the rest of the game quite frankly, are incredibly boring...for me that is.
Enjoy the game whatever way you see fit and don't listen to anyone that tells you different. Regardless of the number of cars you have it's all ultimately about how good a driver you are and you can't rubber band that!!...lol.