Because as soon as you accept another body, janma, birth, then where there is janma, there is mṛtyu, death also. And between janma and mṛtyu, birth and death, there is disease and old age. So Kṛṣṇa says that tyaktvā dehaṁ punar janma naiti: (BG 4.9) "One can avoid accepting another material body." How? Janma karma me divyaṁ yo jānāti tattvataḥ. Simply try to understand Kṛṣṇa, what is Kṛṣṇa, why Kṛṣṇa appears, why Kṛṣṇa takes part in politics, why Kṛṣṇa... so many, Kṛṣṇa's activities.
So this is... Our Kṛṣṇa consciousness movement means: try to understand Kṛṣṇa. Simply if you try to understand... You cannot understand Kṛṣṇa fully. That is not possible. Kṛṣṇa is unlimited. But to our limited knowledge, whatever is possible, that is stated in the Bhagavad-gītā. As far as we can understand about Kṛṣṇa, if we simply understand Kṛṣṇa, His transcendental nature, His transcendental activities, divyam... Janma karma me divyam (BG 4.9). Divyam means transcendental.