The "logical" reason is that I don't believe it would be very compatible with the dual casting system. I believe by creating customized spells, it would cause technical issues with the gameplay mechanics.
For instance, one exploit of the Spellmaking system that I despised, was the ability to fully level up one skill (let's say, Illusion), and mix your Master spell effects with the spell effects of another, untrained school, and be able to use high end spells of your untrained school.
Example:
If I am level 100 Illusion, I can cast a Master level On Target Frenzy spell. This means that the spell is now considered an Illusion spell, thus casting off of my Illusion skill.
Great, right?
But what it also means is that I can combine it with an Expert level Destruction spell. I am a Novice in Destruction.
But because the Illusion effect is greater, the spell works off of my Illusion skill, allowing me to cast powerful Destruction spells well above my level.
Now combine that with the current casting system, and dual casting perks, etc... and you have a mess on your hands.
There's also the fact that, specific spell effects have specific casting types. I.E.: Wards are a specialized, constant casting type. There are constant cast damage streams. Runes. "Hold to cast" spells like Detect Life. Instant casts like summons. Reanimations.
The Spellmaking would get all wonky, as certain spell types would be more customizable than others, leaving certain mages unable to access Spellmaking. For example, what would a Necromancer benefit from Spellmaking, when the reanimate spells are pretty specific in what they do?
You wouldn't be able to customize a bunch of different spells. How could you customize a Ward spell with a Rune cast? How could you combine a reanimate with Detect Life?
The previous system, because it was incredibly simple, made itself much more compatible to Spellmaking. This newer system is much more complex, so Spellmaking would have to walk a delicate tight rope to work properly. It wouldn't be fully customizable like versions past.
And if it's between evolved gameplay mechanics, or Spellmaking, well, I'll take the newer mechanics everytime out.
That's not to say Bethesda implemented the newer mechanics as well as they could. They left out tons of spell effects that should have been in. But out of the 2 choices, they made the right one.
I just don't see how Spellmaking would work with the current mechanics, without being incredibly toned down. Which people would be [censored]ing about that anyways.
Yes, there could be some cool things that could be done with Spellmaking, even with the current mechanics, and I am not against a Spellmaking feature in future DLC. But Spellmaking as we've known it would not work in Skyrim.
QFT. This just had to be resaid. And I agree completely. I was never much into spellcasting, because it appeared very "low end" with the default spells. You basically
had to use spellmaking in order to make something useful, and then there were exploits all over the place. As for lost spell effects - I'm glad glad glad - finally the mages aren't the uber specialists in everything, instead they have been handed a selected toolbox they have to utilize - just like other arch classes. And as for pure destruction mages - that concept sounds bad to me as there is no "pure swordsman" (with
NO other skills to back him up) that would be easy to play either.
Since the invention of magicka regen (now all regen) magic needed a complete revamp, and we got it, and I totally love it. Btw, I didn't miss "spell creation" in Role Master either, and that was a helluvalot deeper in mechanics (for obvious dice reasons) than a CRPG will ever be. Remember other earlier (non TES) games where magicka didn't regen? Even as a mage you had to put some thought into how you're gonna spend your reserve, and potions weren't all that frequent a commodity. Did Gandalf throw spells east and west every 10 seconds? No. Maybe we should start playing like mages and not magic spammers. TES didn't help.