I've long wondered about that. And I'd like to bounce a theory off you. Most people don't start backpacking until their families have had a generation or two of non-physical work. If you work hard all week using your body - construction, laborer, housekeeping, plumber, etc - I think there's less appeal to go sweat all weekend. There was for me when I was doing construction.
With fewer Blacks in the population, and a smaller percentage of blacks getting to college and into professional, non-physical jobs; I've assumed Blacks on the trail would a generation or two behind White backpackers and we're really only had 2 generations of White backpackers now - 70's+80's and then 90+00's. Sure there were some in the 60's and earlier but not as many of all stripes as there are Black backpackers now.
I think of Blacks I've BPed with and they were engineers, MS Music, computer geeks, etc - outlyers in any culture and definitely very immersed in White culture.
And then Scouting is so white - jeez, BSA is 1/3 Mormon and you can't get more White or recently racist than that (I'm referring to LSD doctrine prior to 1978).
And while fishing is a very diverse - Asians, Blacks, Whites - I perceive hunting and its associated camping and hiking as being practiced by a higher percentage of Whites, Native Americans and Alaskan Natives, than Blacks or Hispanics.
What was your entree into BPing? Mine was Scouting, reinforced in University Hiking Club.
And you can leave behind so much of the sunscreen a Celtic sun cancer survivor like me has to bring - you're a natural for UL BPing.