Mainly because the only spell that fits would often be an improved version of a well known 9th level enchantment spell that was altered to have global/omniplanar unlimited number of targets with no save & permanent duration that was cast during chargen.Why not? If it was a spell, it would be guaranteed and no one would think twice about it. Even though magic is merely the fluff that we hang on some game moves.
To me, a PC ability should work as described without needing approval by the GM. If there's clear reason it would not work, okay, so be it... that happens. If there's maybe some doubt about it? We should find a way to explain how it works.
It's a game, right? Before you said you don't like to think of the characters as literary characters... and in the past you've stated you don't like to think of play as a story. Okay... so then let's look at it as a game.
Why should the game mechanics be overridden in this way? Why preserve one player's moves over those of another?
Magic has a lot of limits though