Well, clearly the OP's husband doesn't think the supposed benefits outweigh the costs to his and his family's financial situation and future financial situation.
SAHMs are very costly. The earner has to provide all of the following: shelter, furnishings, appliances, heat, electricity, devices and technology contracts/subscriptions, all insurances, food and beverage, clothing, sundries, personal care costs, transportation/auto/fuel/insurance/parking costs, all leisure, entertainment, dining out, holidays, gifts, Christmas (if celebrated), etc. for a dependent adult. All along with attempting to save for emergencies and retirement.
AND they have to provide all of the above for the children, plus tutoring, extracurriculars, sport, gear, etc., and worry about uni costs.
That is a pretty sweet deal for the SAHM, to get all of the above for low-skill housework and school runs. Oh and of course the "life admin." Eyeroll.
I wonder if they'd like to trade places with the earner, if it's so easy to do?
Meanwhile maybe the breadwinner has a few dreams of their own, such as travel or attending events or hobbies or maybe just not working until they are in their late 60s. They shouldn't have to forfeit everything to accommodate a non-working dependent adult.