I have said above that among peoples who do not till the land marriages were much less fixed, and that it was usual to take several wives. “The Germans were almost the only ones of all the barbarians who were content with just one wife,” says Tacitus,  “if we except a few persons who, not out of dissoluteness but because of their nobility, had more than one.” 
That explains how the kings of the first dynasty had so many wives. Those marriages were less a sign of unrestrained libido than an attribute of dignity : to make them lose such a prerogative would have wounded them in a very sensitive place.  That explains why the example of the kings was not followed by the subjects.