I don't think it's unfeasible so much as it is unnecessary. Kings Island's an extremely walkable park. It's so easy to make that circuit starting with Planet Snoopy, through Rivertown, over to Coney and then ending in Action Zone, stopping off on International Street when you need to. It makes it easy to organize the day and I never feel like I'm walking too far without coming across something that I want to ride. But I could see them being helpful for those who might, say, want to head from Beast/Diamondback over to FoF or Racer without wasting too much time (although if the lines for the Skyride are long, it might be quicker just to make the walk).
At Cedar Point, I'm often thankful for the Skyride because, unless I'm going to hit the Raptor or Wicked Twister, that main Midway is just a hassle. Easier to jump aboard and then when you get off you're closer to all the rides you want to hit.