I can envision a decent proportion of men, at least myself and a few I know, who would find it preferable to have a redundant source of income in the household.
Even if a woman ends up becoming a non income earning partner temporarily or permanently, having one who is capable of earning more can be a desirable trait for multiple reasons.
Well, generally men do the proposing, and as far as I am aware, most proposals are successful. So if the number of marriages are declining, then it means men are not proposing—either they are uninterested in getting married, or they are but don’t reach a point in their relationships where they believe a proposal would be successful. Not sure what the distribution of those is.