Defining Cascade in TypeORM

Why do I need to define the cascade option in the entity which is in relation to the cascaded entity and not in the original entity in itself? For example:

@Entity()
export class Category {
    @PrimaryGeneratedColumn()
    id: number

    @Column()
    name: string

    @ManyToMany((type) => Question, (question) => question.categories)
    questions: Question[]
}

This is an entity named Category Followed by the entity it is in relation with, named Question.

@Entity()
export class Question {

@PrimaryGeneratedColumn()
id: number

@Column()
title: string

@Column()
text: string

@ManyToMany((type) => Category, (category) => category.questions, {
    cascade: true,
})
@JoinTable()
categories: Category[]
}

Why am I defining the cascade option in the Question entity and not in the Category entity?