Send Your Readers Off Now and Then

Speaking on writing well in the vernacular of your subject matter, Mark Tredinnick says this about writing to your target audience:

It's okay to offer readers some words they've never heard before used in the right places to mean what they're meant to mean. Writing can educate in this way, too. Send your readers off to the dictionary now and then. It might remind them to keep one handy (Writing Well, 129).

Why are some translators of the Bible committed to reaching a target audience with an eighth grade literacy level averse to this sort of advice? Would it be all that bad if a reader of the holy Bible had to learn a new word, not least one theologically loaded? Could that be all that bad for that person?