I honestly ask this question myself frequently. But I think it has to do with the vibe of the actual music and not the lyrics. Cuz people don't memorize or really hear the lyrics the first time they listen, they just vibin to the overall track. A lot of the "positive" or conscious hip hop shit has boom bap, out of date beats. It's like I listen to this heavy metal band called Soulfly, and if u just heard the music which is really really really hard, you'd prolly think it's some devil shit cuz it's extremely fast and heavy metal vibes but the lead singer is considered the "Bob Marley of Metal" since his lyrics are actually mad spiritual and positive. And that's why I like it. It's still really hard and he screams in anger but about the injustices of the world, not cuz his girlfriend left him or w/e lol.
I think its the same in hip hop. If you took Waka's beats and added a dope emcee to em, people would listen to it. I think the positive rappers needa just make better music.