>I'm not sure why it's so controversial among digital designers.
Assuming you're talking about the "Give me #000000 on #FFFFFF or give me death!" crowd, it's a kneejerk reaction to the cardinal sin of gray-on-gray content that is fucking impossible to read.
"Kneejerk" is a bit of a down-putting assumption, isn't it? There are many, MANY, reason why someone might disagree with the OP opinion on black and white.
I happened to have a few iOS apps where true black is an option (which is desirable on OLED to save battery). A perhaps less common concern is eInk whose dynamic range is quite limited and for which #000000/#FFFFFF greatly enhances readability.
Assuming you're talking about the "Give me #000000 on #FFFFFF or give me death!" crowd, it's a kneejerk reaction to the cardinal sin of gray-on-gray content that is fucking impossible to read.