Who said they were?The consequences are not the odds.
Yes. It's how action resolution works in (at least) the following RPGs: HeroWars/Quest, Maelstrom Storytelling, Burning Wheel, and 4e skill challenges.'The parameters of the fiction' , is this for reals?
Roughly: the GM narrates a situation; the player explains what his/her PC is doing, and what s/he is hoping to achieve thereby; the GM specifies a check to be made; the check is made, resulting in a success or a failure; the GM narrates the consequence of that check. This narration of consequences is constrained by (i) the action that the PC was undertaking, (ii) the goal that the player was hoping the PC would achieve via that action, and (iii) whether or not the check succeeds.
If the check is the final one for determining overall success/failure of the challenge, then there is an additional constraint: (iv) the GM's narration must be one which closes the scene.
There is room for plenty of mechanical variation within the outline above: Burning Wheel, Maelstrom Storytelling, HeroWars and 1st ed HeroQuest, HeroQuest revised, and 4e skill challenges all have different mechanics, with a range of strengths and weaknesses. But they all follow, more-or-less, the procedure outlined above.
In that procedure, (a) the player's description of what his/her PC is doing has a signficant impact on the outcome, and (b) there is no such thing as "I roll 30, I win, wheeee!". Which is why, given that you are talking about these things which are not part of the procedure, I am asking which mechanics you have in mind in talking about them: the mechanics of some other game that you haven't specified, or the mechanics of some hypothetical game that neither you, nor anyone else as far as I can tell, wants to play?