There are few people who will stay in a relationship with a partner they do not like or respect. Many people have found they would rather be single than settle for less than they deserve. Some people have even begun to realize they prefer being without a regular partner. It has little to do with respect or the ability to care about another person. These people date and find someone they like. It often does not last long because they cannot make a commitment. Serial daters are simply going through the expected motions rather than seeking a true relationship.
It has long been an expectation in society that people will find someone and settle down. Commitment has been an important factor in judging people's fitness for many aspects of life. Careers have been made or broken by the appearance of a person's ability to have a personal relationship with a significant other. The world has changed, and this is no longer a major factor. Being alone is more accepted by the general public as well as employers.
One of the main reasons people have continued to get into relationships is because they want physical intimacy. It has always been a hope that people should grow past one night stands by a certain age. Their friends and family want them to make a commitment rather than having a series of partners. That is no longer true, and many people have found fuck buddies to fill this physical need.
People seeking to stay single will always have physical needs. A fuck buddy is the perfect person for them. They can have no strings attached sex and continue on with their life. Even if they have the same physical partner, there is no need for a commitment by either person. This takes care of physical needs and allows each person to concentrate on the rest of their life.