Some people love the excitement of the chase. They hunt out a new partner every night. They see it as an adventure and are not interested in companionship. Physical intimacy with many partners may be their goal. Some just enjoy the knowledge they can get a new date whenever the mood strikes. This type of person views a long term relationship as a trap. They can feel the walls of a cage closing in on them by the second or third date. That is why they constantly seek new partners.
Finding new partners for each social encounter can become tiring after a while. The hunter needs rest, but cannot imagine spending an evening alone. Connecting with a fuck buddy is their best bet. This is usually a person they have known for a while. Fuck buddies are never interested in a relationship. They simply want a person they can trust for physical intimacy.
This type of arrangement works well for those that prefer the chase to the capture. There is no pretense of a relationship. Both of the partners understand the need for total freedom in dating. They are simply helping each other take care of their intimate needs with no strings attached sex. After their physical needs are satisfied, either person is free to go out and find other people for their social interaction. Buddies like this rarely see each other in public. That is not the nature of their interaction.
There are a select few people that can successfully carry off this type of non-relationship. Many people make the mistake of letting their emotions become involved. This is not a relationship. It is an interaction between two people honest enough to share their need for physical intimacy. If feelings occur, it is time to find a new buddy.