Take two clergymen, a Catholic and a Protestant, both genuinely holy and devout men.
The Protestant is a family man with a job for which he receives a stipend. He has a wife to console and children to nurture. Because of human nature, his flock and even his job will always take second place after his family.
The Catholic on the other hand has no wife to comfort him and no children to bring him satisfaction. He lives on charity and has foregone an earthly family in order to be wedded to his Church. He puts this into practise by devoting all of himself to his parish community which becomes his family, and that is why he is called "father".
H/T to Anthony at Holy Smoke