Atma and "new" body

> When body dies, why is it necessarily a *MUST* for Atma to take new physical body? Is it a must? But for what? If my body dies today, Atma continues to be present anyway. Atma is anyway nitya, sarvagatha.

> When my shirt is worn out, no doubt I *can* change to a new shirt, but that is *not a must* for me. I may or may not go for a new dress. I still exists even without going for a new shirt. Right?

> Another example given is: when light falls on the hand, light is not part of the hand. Light has an

independent existence. So, light never cares whether hand is there or not. Light doesn't go after a "new"/"another" hand, when this hand goes away. Right?

> So, why Atma *has to* take up new body?

> Looking from different perspective, Atma is one and bodies are many. So Atma already exists in so many other bodies too, and number of worn-out bodies are neglegible in comparison, at any point in time.

> Is there any specifications/requirement in nature's law that - at any point in time, Atma has to be in N number of bodies? Something like that? (Sorry for my silly, gross assumptions)

(Sorry for lengthy question. It is just to ensure the completeness of question and to avoid confusions, that may lead to multiple interactions of posts.

Appreciate your thoughts. Hari Om!