I think its also because of the way the AI handles anything. Dwarves writing one paged books, human cities being absolute messes, elves congratulating you for not cutting any trees in a desert, dwarves still holding objects despite the fact that the Burrow is on and a monster is coming right at them at ludicrous speed, etc.
One necromancer writes a book, granted, a one paged book with golden bindings, and one day his tower gets pillaged by dwarves. They take the loot, bring it back to their fortress, put it literally only Armok knows where, one curious dwarf who can read takes it, learns the secret of life and death, then another dwarf takes it, learns the secrets of life and death, then another dwarf takes it, learns the secrets of life and death, etc etc. And maybe those dwarves weren't thinking of becoming Necromancers!
I think the AI in general just doesnt know how to handle anything. Some forts in DF are still active because it's almost hardcoded for them to stay active unless a raid happens. The way dwarves take care of books for example is beyond stupid. I've went to some Necromancer towers, and just saw the bastards, surrounded by their creations, reading books over a whole pile of them. Or have an entire room filled with nothing but books (on the floor, of course). If a player did it, he would have at least made some bookshelves and all, not the Necromancer. The books are just... Lying there.
I think there's also something with the way a dwarf learns things. Now, labor-wise, when he practices something he isn't particularly good at, the more he does, the faster he's learning and improving. However, if he reads a book about the secrets of life and death, boom, he's a necromancer. No practice or anything, he just is now.
I mean, basically, there's a whole lot of things to rehaul in DF, whether its the structures, the way the AI handles them and organization, or the way dwarves make decisions. Tarn talked about it, when he told people about that one dwarf who he tasked to engrave some stone as a way to sum up its experience in his dying fortress, making something beautiful, even though there was a 40% chance he was just going to engrave cheese.