I disagree! We're having the following conversation:
Me: "I want to edit this as a single file, but I can't, because it's slow due to inefficient data structures"
You: "Why would you want to edit it as a single file?"
Me: "Why wouldn't I?"
You: "Because it's slow due to inefficient data structures!"
My point is, I want to edit it as a single text file for creative / process reasons, and there are algorithms and data structures that make this possible, as evidenced by the editors that do let me do it in real time, so there's no real reason not to.
Still, why wouldn't I want to edit it as a single file?