Generally, I would imagine it is because he is not considered the "grandfather of hip hop," as he did nothing to develop the break beat style that defines hip-hop music (other than provide some samples for hip hop artists to use). Blowfly was nothing more than a character - author of such "inspiring" tunes as "My Baby Keeps Farting in My Face," "Shitting on the Dock of the Bay," "Spermy Night in Georgia," and "It's a Faggot's World" (I apologize for any offense, but these are actual titles of his music).
If DJ Kool Herc had passed, you would definitely hear of it.
If DJ Kool Herc had passed, you would definitely hear of it.