Are they dependent on it, or just prefer it because they don't like writing?

What does it matter? They're not writing on their own. All roads lead to Rome with this one

To make the point explicit, Orwell wouldn't find most dystopian the fact your Speakwrite refuses to write anti-state messages, and support the right to subsidized local uncensored Speakwrites. The battle for the public minds was lost when they forgot how to write.