Everyone in my family—by which I mean to include my extended family on both sides—is argumentative. This will likely come as a surprise to no one, though it might be surprising to know that my siblings and I are by far the least argumentative members of the family. It’s important to remember that many couples thrive on conflict. Your lack of arguing might make them just as uncomfortable as their constant arguing makes you.
It does depend, though, on what kind or arguing we’re talking about. While rational debate is one of the best and healthiest things a human can do, malicious sniping is quite the opposite. Many people have trouble distinguishing the two, but it might help you be less uncomfortable if you take the time to see if either of the people in the argument seem hurt by the conflict. If not, what is there with which to be uncomfortable?
That is perhaps what helped me the most when I was younger and getting used to the way my family is. When I realized that none of the arguments surrounding me were malicious, but were instead genuine attempts to exchange ideas and improve beliefs, my discomfort decreased. It can still be a little odd in public; but then again, there’s no reason to be embarrassed just because others can’t appreciate a good thing when they see it.