Even when things weren't fine between the other couples, the men never had to walk on eggshells and be afraid to say "boo" to their spouses. Look at Worf and Jadzia. They had major issues throughout their relationship, but Jadzia never became a haughty bitch because of it.
I think Keiko and Miles would have been a perfect couple to show what divorce is like in the 24th Century. Seriously. Not all marriages work out and having them divorce would have been a great subplot for DS9.