Why does the locale of the race matter to where the dealerships are? The race is broadcast nationally. The amount of people at the race is a fraction of who are watching on TV.
1) Zero sponsor activation possible at multiple events.
2) You're right in that the amount of people at the race is a fraction of who is watching on TV, but they're all still eyeballs and wallets
who are dedicated enough to NASCAR that they bought a ticket that should be interacting with the brand! They can't in this instance because the brand is located far, far away from Pocono, NHMS, Phoenix, Chicago, Iowa, Gateway, et al
3) Hendrick's dealerships are predominantly in the southern US and in complete minority of US states and territories, which makes advertising spend taking place in other places poor for any kind of return. Could you run Bojangles or Krystal commercials nationally? Sure. Do you see Bojangles commercials nationally? No. There is a reason for this.