I watched Wahoo a LOT during the 70's and 80's in various promotions; he's one of my all-time favorites. He was chopping opponents to pieces before Flair made it "cool". Wahoo made the "strap match" famous; I couldn't even begin to tell you how many strap matches I saw Wahoo compete in. Dozens, at least. He wasn't just chops and strap matches, though. Wahoo was an excellent mat wrestler, too.
I don't know for sure why Wahoo didn't wrestle for the WWF. I would guess it's because Wahoo was old-school, meaning he wanted the right to choose his own destiny, to manage his own career, to wrestle wherever he wanted for whoever he wanted. Wahoo was old-school, traveling around from territory to territory, wrestling all over the world. In the WWF, you didn't get that freedom; you wrestled where Vince told you to wrestle.
And on the flip side of the coin, Wahoo didn't have the "WWF look", meaning the steroid muscles and perfectly-styled hair. Wahoo was Choctaw and proud of it but the WWF had the irritating habit of turning ethnicity into (usually) unflattering stereotypes, something Wahoo wouldn't have liked. Wahoo was Wahoo, he wouldn't have "fit in" with Vince's vision of "sports entertainment".
I didn't notice that until reading your question but now that you did...we haven't see the Indian Deathlock since Wahoo's heyday. It would be nice if now and then somebody would slap a Deathlock on an opponent and give a little shout-out to Wahoo.