There are many good reasons for relationships to end. Sometimes the problem is that the couple is not really compatible. While they may really like each other, their goals in life may be too different for them to overcome. Breaking up will be a relief for this couple. They may be able to easily overcome their differences and remain friends. This is one of the best case scenarios when dating, but it does not happen very often. Many people end up breaking up because they find out their partner has been cheating on them.
A person that cheats on their partner is also cheating themselves. They have a lack of trust, but do not realize it is because they cannot be trusted. A person that chooses to cheat should not be in a serious relationship where physical intimacy is expected. They should choose to only date casually. When physical needs arise, they can always find a fuck buddy to satisfy them. This separates dating from sex and allows them the best of both worlds.
People that choose to be fuck buddies are not interested in committed relationships. They want only physical satisfaction from a partner. Rather than waste time and energy on something they don't want, they choose a person for no strings attached sex. This gives both people physical relief without worrying about whether or not they are seeing anyone else.
Being in a relationship requires commitment. For those that cannot make a real commitment, staying out of relationships is best for everyone. Dating casually while working through their issues is the best way to resolve the problem while still maintaining a social presence. It is a way to be a thoughtful and caring person without worrying about the necessity of hurting people by cheating on them.