We could. We could make you succeed in an Intelligence (Spellcraft) check, with a DC based on the level of the spell, in order to cast any spell. I'm pretty sure that it would be bad for gameplay, though, since it would give most spells two independent chances to fail....
What I was saying is that it's much harder to justify a Fireball, once successfully cast, that fails to have any effect whatsoever on someone in its area.
That's what I'm saying. Part of the disparity between mundane and magical abilities comes from the narrative.
Since we've decided that we want the wizard to throw around huge explosions, it's hard to come up with a reason why that wouldn't be unavoidable; but any fighter is limited to mere swords and arrows, where it's hard to justify why it would be unavoidable.
That's why there's a double standard.
I think we're getting some topic drift, here, so I've quoted both the post that started this fireball digression, and your latest reply.
The original issue was whether there was any potential problem with having casters have a chance of failure when they used a spell, instead of the spell working automatically. We considered the issue of it adding a roll to the resolution process affecting playability - but, between the possibility of using the casting check as the result of any other check called for (like an attack roll), and the fact that spells can already call for many checks (such as saves) anyway, I think we can agree that isn't a major impediment.
Then, you brought up Fireballs and the possibility of it failing to have any effect "once successfully cast" as a possible objection to the idea of such a check.
AFAICT, nothing suggested as a way of implementing such a spell-failure check would result in someone standing, unharmed, in the midst of a successfully cast fireball.
Now we've lost track of that issue, and circled back around to somehow justifying the OP-double-standard with the narrative of magic, yet again, even though, as magic isn't real, and can be narrated in any way desired, there is no narrative foundation for magic being modeled a certain way. Thus, that narrative can be subordinated to game balance and playability.
If, for some reason, we wanted a fireball that had a chance of doing no damage at all, even when successfully cast, it would be trivially easy to narrate it in a consistent way. Magic, just for one instance, could be a matter of imposing will upon reality, and, while the mage could conjure a fireball without much resistance from reality, getting it to actually burn anyone could require overcoming /their/ will, with a strong-willed/courageous enough individual being able to walk through magical flames with no effect. Or, it could be unable to affect the 'pure of heart' or 'righteous' or something else. Or, the flames of a fireball could simply be inconsistent in how concentrated they are in different parts of the affected area, allowing the skillfull to avoid them entirely. Conversely, the area could be filled with magically-inescapable flames that burn anything (even stone, metal, water, disembodied spirits or other flames) and just do a set amount of damage, regardless, and that, too, could be justified by the narrative.
So if narrative justifies a double-standard, that double-standard should be that the narrative of magic is entirely subordinate to balance & playability.