When a partner gets a job far away, the couple generally tries to cope with a long distance relationship. These two people will spend hours on the phone or video chatting. They may email each other several times a day. A person that likes to cuddle and be physically close will miss the physical aspects of the relationship the most when their partner is far away. They often find that having friends and family around is a great comfort, but it is just not the same. The missing physical hugs and cuddling may overwhelm their need to stay with their current partner. This person will often come to the painful realization they need to end their long distance relationship.
People that have been in a relationship for a while are often close and have much in common. Hurting the other person by ending the relationship is not something they do easily. Honesty compels them to let their partner know they cannot live in this fashion. Both will find better lives in the end, but it is still difficult when the breakup occurs.
Ending the relationship also ends the possibility of physical intimacy. A person that craves the touch of another might be happier with a fuck buddy at this time. They will still be hurt over their breakup and not ready to find a new relationship. No strings attached sex is only for their physical needs and gives them time to mourn the loss of their distant partner.
There are very few relationships that survive well when one partner travels. Fuck buddies are a good temporary replacement until it is time to find a new partner. They provide physical intimacy without the pressure of being in a relationship.