NASCAR is not a combat sport, nor is it the most simple. Anytime you have a sport that requires effort to understand the intricacies, you will have individuals who put it down. Two similar examples are water polo and cricket. For the people who take the time and effort to understand NASCAR, it can be very fun. I have been to several races, and the most fun is when you camp out with friends and experience it in person. I thoroughly enjoy the Bank of America 500 just about every fall, because I get emotionally invested in the experience. Those who don't will typically not receive the same entertainment.
I've never understood car racing and think it is incredibly boring. The only part I find mildly entertaining is when they crash; however, it's certainly not enjoyable if someone is seriously injured as a result. Because of that, I don't think it's fun, but I have no problem with people who love the sport.
No, watching NASCAR is not fun, because if I want to watch traffic, I can just drive around until I find a traffic jam. NASCAR is also dangerous and a lot of people die doing it. NASCAR is also very loud. I can go blast my ears out in traffic anytime. I don't need to buy a ticket for NASCAR.
Nascar has to be the most boring sport in American history. There is nothing fun about sitting for hours on end watching cars make left turn after left turn. I think the only thing that may make it worth watching for some people, is the possibility of seeing a wreck.
I would much rather watch paint dry before I would watch the races. For me, it is about as entertaining as watching the grass grow. I know there are tons of people who do enjoy it and that is alright. Whatever floats your boat. For me, not so much. It is very boring indeed.