This all goes back to game balance. A first level wizard can't cast ninth level spells, is there a reason a first level fighter should be able to use whirlwind attack?
The immediate response would be "Well, ninth level spells are simply too complex"... but that's really just a fluff reason. Power Word Kill is (presumalby) one word. You can create any reason you want for why a ninth level spell is a ninth level spell, but it comes back to balance.
Even if you start handing out penalties for things, eventually those penalties will become a nonissue in the grand scheme of things.
Consider "Robilar's Gambit" from PH2 (if i recall correctly). This is actually a very potent tool in the right hands. Every time your enemy attacks you, he provokes an attack of opportunity.
Then there's the epic level handbook feat that allows every attack of opportunity to be a sneak attack.
See where I'm going with this?
Let's say you got Robilar's gambit pre-requisite free... and the DM gave you a -6 penalty to attack... and you got to use that epic feat free... with another -6 to attack... and we'll even add a fumble on a 2 or a 1.
Well just use a brilliant weapon and all your attacks become touch attacks for living material... entirely negating the -12 penalty you were taking and ensuring everytime anyone ever swung at you, you'd have an opportunity to do massive damage...
Is there any difference between Robilar's Gambit and Whirlwind Attack? or even called shot? Not really.
Those prereqs are a must, however... to ensure balance.
The immediate response would be "Well, ninth level spells are simply too complex"... but that's really just a fluff reason. Power Word Kill is (presumalby) one word. You can create any reason you want for why a ninth level spell is a ninth level spell, but it comes back to balance.
Even if you start handing out penalties for things, eventually those penalties will become a nonissue in the grand scheme of things.
Consider "Robilar's Gambit" from PH2 (if i recall correctly). This is actually a very potent tool in the right hands. Every time your enemy attacks you, he provokes an attack of opportunity.
Then there's the epic level handbook feat that allows every attack of opportunity to be a sneak attack.
See where I'm going with this?
Let's say you got Robilar's gambit pre-requisite free... and the DM gave you a -6 penalty to attack... and you got to use that epic feat free... with another -6 to attack... and we'll even add a fumble on a 2 or a 1.
Well just use a brilliant weapon and all your attacks become touch attacks for living material... entirely negating the -12 penalty you were taking and ensuring everytime anyone ever swung at you, you'd have an opportunity to do massive damage...
Is there any difference between Robilar's Gambit and Whirlwind Attack? or even called shot? Not really.
Those prereqs are a must, however... to ensure balance.
