The idea is to give all males in society equal opportunity for a reason to fight for the Republic (a wife); so to say the least, the reasoning behind the idea is dated (Augustine). So the issue really boils down to how well natural law and man-made laws cohabitate in practice throughout society. Marriage, as an institution, is important. It's a proven model among those disciplined and reasonable enough to see it through. The machinations of the current society work against every aspect of family and child rearing, though.
Is this an expose of human nature, or of that of the greedy influencers and controllers? Perhaps a bit of both? Should there be laws dictating marriage, though? Of course not. It really is a strictly religious institution that the gov't has, yet again, completely interjected itself into. The current world might not be ready for what a truly functional (in accordance with nature and a cooperative society) civilization would look because understanding the totality of how the emotional and rational mind interfaces with actual reality.
Jacob had two wives because he understood human nature. They've taken much more from humanity than humanity even comprehends, right now.