Fear of commitment
Fear of commitment, also known as gamophobia, is the irrational fear or avoidance of long-term partnership or marriage. The term is sometimes used interchangeably with commitment phobia, which describes a generalized fear or avoidance of commitments more broadly.
In essence, despite deriving satisfaction from companionship in a relationship, people may choose to distance themselves and withdraw if the relationship progresses to a serious level of commitment.