Some say it's because she's an attractive woman and a sponsor's dream. Some say it's because she's hurdling barriers no other woman has in racing.
Some say she lacks talent. Others say she has already proven that isn't true.
But one thing is undeniable. Anywhere Danica Patrick goes, excitement follows. Autograph seekers, adoring fans and detractors do, too.
Any event in which she participates - even if it's just a visit to a NASCAR Sprint Cup team's race shop - matters. Any race in which she competes is relevant to more than just the fans of that race.
That's why NASCAR needs Danica Patrick. The only woman to ever win an IRL race would elevate fan interest and excitement and bring money and a powerful appeal into the all-male club.
"If she could come here to NASCAR and create the excitement that she's created in the Indy cars, that would be huge for NASCAR," Carl Edwards said last month. "And I think anyone would welcome her as a teammate, and I know she's talked to a lot of teams. It could be big."
The sports world hasn't escaped the recession. Not the NFL, whose commissioner took a pay cut this year. Not the NBA, which lowered its salary cap and luxury tax limit, and predicted further cuts and dips in revenue next year. NASCAR, a sport heavily reliant on advertising and sponsorship dollars, has felt the impact sharply.
Preseason predictions about major teams shutting down and fields being incomplete didn't come true. But there have been layoffs and budget cuts. Fans aren't filling the stands at the rate they once did.
Indianapolis Motor Speedway still has tickets available for one of American auto racing's most prestigious races this weekend. It doesn't help that a year ago fans came to Indianapolis and tires exploded every 10 or 12 laps, leading to cautions throughout the race. Although Goodyear feels confident it has solved the problem, fans are wary.
Ratings have also suffered.
"It's fair to say that we certainly recognize that the baton is being passed to us with ratings down," said Julie Sobieski, ESPN's vice president of programming and acquisitions. "We're doing everything we can from a TV standpoint."
NASCAR is making a serious effort, too. For example, it added double-file restarts to make races more exciting.
The country's most popular female racer and its most popular motor sport would give it a jolt of positive publicity and energy.
Patrick is the most visible driver in the IRL. Sponsorship drives racing, and sponsors pay for personalities.
Patrick isn't a magic wand. Her presence wouldn't turn around the economy and bring back sponsors in droves. Her entrance into NASCAR wouldn't fill race fans' wallets with expendable cash they can take to the track.
And she can't show up and falter. Once the novelty wore off, who would care about a driver who couldn't compete? Does anybody watch the Indy 500 to see Milka Duno finish 20th, as the Venezuelan driver did this year, or Sarah Fisher finish 17th, as she did this year?
But with the right training and development in stock car racing, Patrick could be a competitive NASCAR racer in a few years.
"Nobody knows for sure what level of talent she's got as far as a stock car until she actually just gets in one," Tony Stewart said. "If she's serious about it, I don't know if she needs to get in a Late Model first and run some laps and then try to get back to a radial-tired car."
And once she figures out stock car racing, she will be one of NASCAR's biggest stars.
The money will follow Patrick from the Indy Racing League right into NASCAR, and so will the fame and the superstar aura. The little girls and grown men, and those in between who hang on her every move, they'll all pay attention to NASCAR.