Ironically for a motor racing series, it's the spiralling cost of fuel that is really hurting NASCAR: US gas prices are approaching $4 a gallon, minuscule by UK standards but practically a national scandal in the land of the automobile. It means that people are cutting back on car travel and not venturing so far, and when you have a sport that relies on pulling huge numbers of people in from a wide catchment area to come to events, that's a big problem.
For Dover, a bad weather forecast was another problem that persuaded many potential fans to stay away. "Dover had a tremendously bad weather forecast," NASCAR's chairman and CEO Brian France said. "It's a miracle on Saturday and Sunday that they got the races off at all. We certainly don't want to see empty seats.
Charlotte hosts two Sprint Cup events - one in May, one in October - together with the All-Star Race. That's a lot of events for a region to support when you're trying to fill in a stadium with upwards of 135,000 in terms of seating capacity, especially in a series with 36 races during the year week in and week out in and around the same southern area of the US.
F1, by comparison, typically holds just one race per year in any given country, and makes a point of positioning a Grand Prix as a major "don't miss!" national sporting event. Last week's Grand Prix in Spain was one of the few times where there will be a second race later in the year (at Valencia), and the downturn in crowds at Barcelona - despite the star pulling power of former world champion local here and superstar Fernando Alonso in a Ferrari - deeply concerned race promoters.
Spain put last weekend's race day attendance at 78,130: by contrast, the "disastrous" attendance at Dover for mid-May's FedEx 400 was nonetheless higher, in the region of 82,000 despite the slump and the fact that it's the lowest attendance there since attendance records were first disclosed in 2003.
It's not just Spain: the Malaysian Grand Prix struggled to reach its target of 65,000 race day tickets, despite tickets costing as little as £11 ($19). And the future of the Turkish Grand Prix is in doubt after estimated attendance figures slumped to around 35,000.
Compared to that, figures of 82,000 for Dover are practically stratospheric, however much they're down on previous years; it's just that the crowds are not as big as track owners hoped when they expanded their circuits in the 90s and early 2000s, and today's attendance is overwhelmed by the capacity, hence the trick of resorting to temporary advertising banners.
The All-Star Race attracted attendance of 115,000, the same as a capacity crowd at Silverstone - impressive even if the empty seats in the 140,000-capacity stadium were painfully evident on TV. Things could be a lot worse for this coming weekend's regular Nationwide and Sprint Cup season races: while the "All-Star" event is a one-off with a crowd-pulling $1 million prize winner at the end of it, promoting "Round 12 of the weekly Sprint Cup season" is a hard sell in these austere times when even premier F1 Grand Prix races struggle.
The decline in figures is leading NASCAR to revaluate where it runs, how often - possibly even the very format of the Sprint Cup season. Can Charlotte really host two Sprint Cup races (and the associated Nationwide and Truck events) a year, plus the All-Star? Should the All-Star Race go "on tour" and be shared around other tracks across the country?
And what about Dover, which also has two May/October events on the NASCAR calendar: if it's struggling to top half capacity each time (with the later Chase race understandably attracting more interest), maybe it should only host one race so that fans can save to afford to come to that rather than split interest between the two? But even with reduced attendance, the races are still vitally important to keeping the facility open at all: losing an important event could mean the entire facility becoming economically unsustainable, and being forced to close.