it explains why your wife is in Louisiana in the first place, what she was doing on the ship, and how it created the little girl (and what she's capable of). Secondly, it throws the player a curve ball. By that point you've got used to having a variety of weapons on you. Now you have to explore a place you've never been with nothing to defend yourself. It's a great way of having the player lose their abilities, certainly better than a Metroid Prime style "you fall on your head and everything you've learned falls out". It's also scary, which is generally the point of an RE game. The video tape sequences do the same thing, they let you explore the story without having to do anything as crass as finding, say, Daddy's diary or something equally contrived. Letting the player be involved in the plot is better than flat out stating it in a cliched audio log, or taking away control in a cut scene.