There are many physical and spiritual reasons why ejaculation should be converted into non-ejaculatory whole body, brain, and heart orgasms.
But there are also relational reasons.
When a man has no control over his ejaculation, he cannot meet his woman sexually or emotionally. She knows she can deplete him, weaken him, empty him of life force. She has won.
When a man ejaculates easily, he creates ongoing distrust in his woman.
At a subtle level, she feels he cannot be trusted. She, and the world, can deplete and depolarize him easily. This subtle distrust will pervade the relationship.
She will not only doubt him, but actually act to undermine his actions in the world. By undermining him she demonstrates and tests his weakness, but she also hopes that through such tests he can learn to remain full.