It was a way to win without having to devote a card to actually winning the game
I feel this is a direction that modern MTG has shied away from in recent expansions, though I'll save that rant when we get there
If your only cunning opponent controls Runed Halo with Gifts Ungiven chosen for it, or controls Leyline of Sanctity and/or similar cards, you cannot cast Gifts Ungiven, since you cannot target your opponent with that spell, and you may not target yourself
You're making an investment when you can Profound Journey, but one way to mitigate the costs of this investment is to return a permanent with a large immediate impact on the game
With Spider-Man in the mix, they get a lot more attractive
Mirage is an important set for Commander players