There are women who do this too and also for the same reason. It's about power.
"If I can keep you interested, invested, and chasing me without ever having to fully commit to you, then it means that I have the power to control you. And I don't want to be in a marriage unless I can control my spouse. Because I don't want to feel emotionally vulnerable and fear that they might divorce me."
A marriage from this type of dynamic is always one-sided because one person has been trained to be the codependent partner. What basically happens is that the more narcissistic partner will use the excuse, "I want to work on my career, myself, etc. I don't have time to be in a fully committed marriage with you, but I'm open to playing house. And if things don't sour too much between us, I'll consider marrying you."
Since the more anxious partner is in love with the potential of the relationship, they latch on. Anxious people tend to have lower self-esteem so they fall for the more narcissistic person's lovebombs, future faking, and delusions of a happy pairing. In addition, narcissists are masters at selling themselves to be the perfect boyfriend/girlfriend who will become the perfect husband/wife. That's the whole reason for the lovebombing phase where they're extremely attentive, helpful, showing grand gestures - the kind of behavior that is usually exhibited only when in a fully committed relationship. They're marketing themselves. "This is how it will feel to be in a commitment with me, if I choose you."
The anxious person is sold! They become addicted to this potential future. Meanwhile, the narcissistic person always keep their options open.
If the anxious partner passes the test during the grooming stage by not demanding too much or becoming too overwhelming to the more narcissistic partner, then that's when a marriage could happen. But most often than not a breakup will always happen. The anxiety becomes too much, triggering the anxious partner to become more and more jealous, insecure, and "problematic". But remember, they don't become that way all on their own. The more narcissistic person orchestrates that by using push and pull, hot and cold, energy.
The anxious person's tantrums will be the perfect excuse for the narcissistic partner to end the situationship. They realize that their goal of having a one-sided relationship where they have all the power will not be possible with this person and therefore, they need to move on from this "crazy, toxic" being.