As to why a number of Black Americans are 'in to' blues or-for that matter-jazz, I'm sure there are many reasons that could be given for this.

Among those reasons, I would suggest that we {African Americans} have a strong preference for social music to be performed with couple's or group dance {as in line dances like the "Electric Slide" . I think this ties into the importance of participatory/community nature of art in African cultures. That participatory nature of the creative experience includes the audience calling out encouragement or singing along with songs..
but I don't want to digress...

In my opinion, when dance became separated from the performance of the blues and the performance of jazz-when these two musical genres became performance and listerner only art, that spelled the demise of blues and jazz as music to be appreciated by and supported {through record purchases/concerts etc]for the masses of African Americans.

Perhaps other populations are more enthusiastic about blues and jazz because those populations don't traditional have as integral a tie between dance and music as African Americans and other people of African descent.