Kind of a depressingly old list, isn't it? Really shows you how NASCAR-centric racing has become for American drivers. I would have loved to have seen Jeff Gordon competing in F1 or Le Mans, and it's hard to rate him higher without that kind of experience.
1. Technology: The skill set needed to drive a rear-engine, high-downforce car now -- as compared to the 1970s -- is significantly different than a front-engine, low downforce or high horsepower-to-weight ratioed car. Blame engineers, wind tunnels and exotic composite materials if you wish.
That's somewhat the reason why some midget and sprint car drivers found more success in NASCAR than open-wheel racing. And why Danica Patrick (see also Dario Franchitti, Sam Hornish, et al) knows how to point the nose and hold the pedal down, which works in qualifying at Daytona and Talladega, but she doesn't have the car control to run on the edge while feathering the throttle. That the skill Gordon and Stewart brought from USAC dirt track racing.
2. Money: During NASCAR's heyday, owners were signing dozens of young drivers to "futures contracts." Why spend years in Formula Fords and Indy Lights, hoping to catch someone's eye in open-wheel when most of the owners there are hiring failed F1 drivers and Brazilians -- unless you bought a helmetful of your own cash or a sponsor. If Roush, Hendrick and Gibbs were willing to pay you $150,000 a year to drive Late Models or maybe a couple of Truck or Busch starts, you couldn't turn that down. However, that's gone, so the ladder to NASCAR isn't very well-defined right now.
3. Sponsors: The name of the front of your driver uniform means a lot more than the one on the back. If Honda isn't in NASCAR, they don't want you racing in a Toyota at Darlington. It's not that drivers wouldn't like the opportunity to cross over -- they can't without negotiating a mountain of paperwork, bringing in a bevy of lawyers to protect a bunch of motorsports executives with massive egos and fiefdoms.
It was enlightening to see McLaren allow Alonso to run Indy in a non-McLaren car. That's rare in this day and age.
4. Opportunities: There may be no more than six cars on an F1 grid with any reasonable hope of winning. None of those have much interest in hiring an inexperienced American to sit in a billion-dollar race car. Michael Andretti was probably the best hope in the past three decades, and that ended poorly. A lot of talented American drivers have gone to Europe and run F2 without a sniff of a big-time ride -- thinking specifically about Alexander Rossi. Ferrari gravitates toward Italians, Williams prefers English drivers, and so on. The Haas team has shown absolutely no interest in grooming a Ryan Hunter-Reay, Josef Newgarden or Rossi. Their loss.