(Post linked via someone on my lj flist, irksome narking about this in the comments. Duh.)
But The Crimson Petal and the White is not only set a good decade before Jack the Ripper was prowling the streets of Whitechapel, but in entirely different areas of London. His activities were really very localised in time and space.
So that's why no-one was likely to be mentioning him in CP&W.
Plus, actually there was a huge range of prostitutes in Victorian London and not all of them were doing it against a wall for a glass of gin in the East End slums.
So please, commenter over there, not to be quite so sniffy about its historical accuracy from a position that's not quite as superiorly knowledgeable as you imagine.
ETA This seems to me to be the 'all the past was happening simultaneously' fallacy.
My sense is that Michel was actually being very specific about when CP&W was set: AND mightn't any srs writer working on this subject want to avoid the obvious? Esp as has been done (Wedekind/Pabst/Berg's workings of the Lulu story).