I think with any product, the question is: what can you do with it that you couldn't do otherwise?
With the iPad, the only real answer to that is "use it while standing". So for anyone who has to take notes or reference things while standing, it's perfect. But for everyone else, you're better off using a laptop: better keyboard, better OS, built in stand, etc.
With the Vision Pro I guess it's about the VR experience. You can't have a stereoscopic, immersive experience otherwise. So the next question is why you want a VR experience? I guess gaming is a big one, but gaming is one thing Apple doesn't do for some reason. So maybe watching movies? But that's not the best alone, so again, not quite sure about that one. What's left? Productivity? I guess working in 3D and having some very niche workflows would benefit from it. But that's maybe like 0.01% of people.
It's also not practical. You're not going to take it with you everywhere, and you're not going to use it anywhere. This is mostly a "use it at home only" device. You also can't use it for very long, so it can't replace any other device. You can use a computer for 12 hours, but not this. So whatever amazing immersive workflow you can use the Vision Pro for, you'll have to switch back to using a regular computer pretty soon.
I'd think the only thing you'd only want to do for 2-3 hours a day, at home, alone, is watching movies and playing games. Or just buy an enormous TV for half the price, and you can even share it with other people.