Firstly, let's acknowledge that techno is a specific genre of electronic dance music, instead of the popular, yet mistaken, catch-all term for instrumental electronic music. Similar to how not all hip-hop is hyphy, drill or boom bap, but those 3 are all subgenres of hip-hop.
As to 'why black people are not into techno'...well, I'd say that there aren't a whole lot of people into it, at all, and that it mostly remains a regional thing, in which black folk certainly listen to, participate and engage in that scene.
It should also probably be remembered that because entertainment and art have been one of the few institutions more or less continuously available to black access in American history, black culture emphasizes and encourages artistic expression in ways other racial groups do not. Virtually every form of popular music can be traced back to the black community. This includes rock and roll, blues, jazz, hip-hop, r&b, house, techno, funk, and soul. You could even make an argument for punk, country and folk. Some of these genres have been co-opted, exhausted, replaced, or popularized, but some of them always were a specific expression adopted regionally. Just because a couple hundred or thousand black folk in a Northern urban center created a subgenre 30 years ago, doesn't mean that it will be adopted elsewhere, or even appreciated.