Just Wondering

Marriage is hard. Anyone who tells you otherwise is lying. 24/7 proximity and seeing close at hand each others faults makes the relationship difficult. In the old testament there was polygamy and concubines. I can't imagine a second wife, but most men will admit to being attracted to other woman and even having connections to women either at work or other places. Men have affairs all the time and I just wonder if God had no clear ordinance against keeping a concubine how many men would jump at the chance.