Because, in a dark room, the light can still pierce through the eyelids. That's not exactly foolproof. Not to mention that it's an important scene, and missing on what the scene is supposed to show would be missing out on a crucial plot point (I've heard about this particular point via people who've read the book, which many people have called a clusterfuck of a final part of the saga, so yeah).

And @caseh, there's also a danger for people who have not had any seizure history. It's not like you can predict this stuff.

With how widespread this is becoming, as well, Summit needs to say something rather soon as to how they intend to address this situation. Remember what happened to Electric Soldier Porygon the day after we heard about the seizure incident in Japan, and how much fixing of anime happened as a DIRECT result, and that was in SD! Imagine how it would've been now in HD, as this movie is now, or worse yet, in 3D! Would've been a disaster!

So yeah, something needs to be said before this gets out of control since there's more reports of issues DIRECTLY related to THIS scene!