In "The Rocking-Horse Winner", why is Paul's mother left unnamed until the very end of the story?

Generally, when an author leaves an important character unnamed it is to make the character universal. In other words, Hester could represent any materialistic mother. In "Rocking Horse Winner", the identity of the woman for whom Paul is ruining both his physical and mental health remains a mystery and this reinforces the mystery behind Paul's actions. The audience wonders what kind of a mother would be so self-centered that she would not notice the changes in her son or wonder where the money was coming?