To jump back in here, I think the details of the marriage contract probably vary by state but if I’m not mistaken, all 50 states a) view it as a lifelong contract between the two partners and b) consider all finances between the couple as joint property. It doesn’t matter if the partners provided 50/50 or 90/10 - the sum of their property and their lifestyle belongs to both of them jointly.
So this husband made a life long contract with the wife and agreed that the sum of their earnings would be shared jointly. He legally & voluntarily made her these promises and assumed these obligations.
So now he wants he out of his contract. Well it’s no different than any other contract or business arrangement, is it? The party that wants to break the contract can’t just say “I changed my mind” and skip off merrily leaving his obligations behind. The husband can get out of his contract - but there are penalties and obligations that apply to anyone who breaks a contract. They apply in marriage contracts too.
Anecdotally, for what it’s worth, courts are more likely to award alimony type payments to spouses that have been “wronged” in some way. If he’s been sleeping around then the courts’ might be more sympathetic to her needs than his. Human nature, I suppose.
And yeah, all of the above does (and should) go both ways.