This is not always easy for both partners
The purpose of open relationships is to give each partner the freedom to seek physical intimacy with other people while remaining in the relationship. This is not always easy for both partners, and some of them may choose to find only one person to share their physical adventures. A fuck buddy is a perfect fit for this person because they are not interested in a relationship. Their only desire is to be physically satisfied, and their interest in any particular partner stops when that is done.
It is not difficult to find fuck buddies in the modern world, and there are online sites that specialize in matching people in many different ways. People looking for an intimate partner need only log online and search. After that, it is simply a matter of finding a person who is compatible. It is up to the two people to figure out the terms of their private arrangement. A buddy is often amenable to most arrangements, but they might have a roommate and need to meet elsewhere.
Modern society asks few questions about personal relationships between couples. As long as both are satisfied with their life, it is considered rude to pry into their business. People with open relationships are more adventurous than most, and having no strings attached sex is part of the attraction. Their lifestyle is shared by their partner, so issues such as jealousy usually do not arise between the couple. As long as they keep their private lives off limits to others, society needs to never know about their intimate habits.
Compatibility comes in many different forms, and couples need to be able to express their desires to their partners. Intimate needs should always be thoroughly discussed for a healthy relationship. While an open relationship might seem odd to people with traditional relationships, a couple that truly wants this lifestyle can be just as happy.