I suspect the reason the riders on the road were largely white had to do with money. It’s a luxury, and whites tend to have more disposable income.
Plus, to care about Route 66, you have to love America.
And minorities are taught to hate America.
(For the record, my father, who was an accidental American like myself, having make his home in Israel, toured Route 66 with my mother, his wife, 10 years ago -— because he loved America and wanted to see it.)
Greyhound don’t do Route 66. I suspect the numbers would be pretty similar on US 12 near my home.
My folks did the Route 66 thing for their honeymoon in ‘63 (in a Volkswagon Beetle!)
Thanks to the movie “Cars”, my kiddies think it would be the coolest thing ever to take a Route 66 roadtrip.
After seeing the demographics, looks like a safer trip than the usual Florida vacation!