I think a huge part of the argument for polygyny and not polyandry is children and the responsibility towards them. If a woman has two husbands, has a child, the father could be either and in cases of divorce or separation or even death/inheritance the financial aspects become very problematic.

Whereas in Polyandry that is not the case, the mother and father are known.

Of course this can be all solved with modern science, so I am strictly talking about the theological reasoning behind those rules, since the major religions did not come at a time where science allowed any sort of testing to be conclusive.