Even in a society which freely allows men to take more than one wife legally, not all men will do so. Rather, only a few should and only a few do. Two factors weigh most in this regard. The qualification of the men, and the number of women in society in need of protection. There are two types of men who are qualified to take more then one wife. One are those who are very wealthy and can financially take many wives, as in the case of kings or very wealthy businessmen. The other are those who are qualified in the spiritual sense, the brahmincal sages, who are able to lead their dependents out of the cycle of birth and death. A Vaishnava who can take his dependents to the Lotus Feet of Sri Krsna is qualified to take on a larger number of dependents, if he so desires. But, he must also be able to maintain his wife or wives to the standard of his ashram. At least the wives must not be forced to work out side the home, working as sudras or servants of others, they must have food, shelter and clothes, at least to the standard of the ashram of the husband. Not that if a brahmana marries more then one wife the wives must be cared for to the standard of ksatriya queens. Brahmana may live very simply, still, each wife must be taken care of respectfully and not be in want of basic needs.
Brahmanas, especially Vaishnava Brahmanas, are generally not at all wealthy, so if they take more than one wife, they generally can take only 2 or 3 wives or so. More worldly men who have great wealth can materially accommodate a large number of wives and offspring. It was not uncommon for kings to take a 100 wives or even 100’s.
The society benefits when a wealthy man takes many wives, and also so do the wives. These women will be materially well taken care of in this life. The society benefits because these women be protected from falling into a life of illicit sex and prostitution, which keeps society focused in the mood of mundane goodness. The children these women will have will be provided for. They will be wanted children, and come into a loving and caring environment.