Rebecca doesn't have too much good to say about marriage. Matrimony is presented as necessary for social and economic respectability. Some people call this gold digging, but in this story, it's more like status digging. In this story, Maxim, Rebecca, and Mrs. de Winter are all willing to do anything to maintain the appearance of a successful marriage, and seem to see a failed marriage as a fate worse than death. Literally. Think about it: our narrator almost jumps out a window to her death in order to avoid the possibility of a failed marriage. Now that's a lot of pressure.
Maxim and Mrs. de Winter both have too much baggage; their marriage is destined to fail.
Maxim and Mrs. de Winter's shared secrets will bind them and strengthen their marriage.