2 points
It’s because people can’t read it as fast as people talk. Or, the dub has to match up the mouth movements, but the subtitles don’t.
I watched a fan-subtitled anime a long time ago, where they literally translated every word. It was like a paragraph of text on each screen, and it was impossible to keep up with.
Good points, but even so I’d still rather have a less-than-optimal sub that still lined up with what the characters were saying in the dub, than having the two conflict with each other. (Maybe if you turn the dub off, the subs could be replaced with the better sub-only version?)
