(Warning: This post is hardly groundbreaking or newly-insightful in nature. I'm definitely late in the party; yes, it's taken this far until the Oblivion modding tools work reliably for me in Linux. =)
In May, I rambled about how this newfangled need to do physics modelling makes games sometimes less intuitive.
Now, I might go ahead and ramble how new more advanced game technology makes modding harder.
When creating newfangled adventures in most games, creating talking animals has traditionally been extremely easy if you have the modding tools. Just plop a copy of a creature to the game, make the thing non-hostile if necessary, and add a dialogue. Right? That's how it works in Neverwinter Nights, at least, and from what I know, in most older games. Sometimes the "copy of a creature" entails some extra work, but it should be doable, right?
Wellll... The Elder Scrolls IV: Oblivion respectfully disagrees. You see, in Oblivion there's difference between "creatures" and "NPCs". The biggest difference, of course, is that creatures cannot engage in dialogue.
So we're deep in the "'copy of a creature' entails some extra work" territory: In theory, we should be able to copy the meshes, stats, stuff, etc to a new NPC. Not so! No! Apparently, you need to do some odd extra legwork to make the creatures talkable.
And when you really think of it, what's the big reason for not allowing this at engine level, right out of the box? Why, the new improved dialogue system, of course, the facial animation system in particular. So, the engine designers went for a trade-off: Talking things need to be redesigned to use the new improved system, while non-talking things can use the old boring way of doing things, which needs less overhead.
No talking mudcrabs here...