When He met Śrī Rāmānanda Rāya on the bank of the Godāvarī, the varṇāśrama-dharma followed by the Hindus was mentioned by the Lord. Śrīla Rāmānanda Rāya said that by following the principles of varṇāśrama-dharma, the system of four castes and four orders of human life, everyone could realize Transcendence. In the opinion of the Lord, the system of varṇāśrama-dharma is superficial only, and it has very little to do with the highest realization of spiritual values.
(Srimad Bhagavatam--introduction).

Śrīla Śukadeva Gosvāmī was a Vaiṣṇava from the beginning; therefore, there was no need for him to undergo all the processes of the varṇāśrama institution. Ultimately the aim of varṇāśrama-dharma is to turn a crude man into a pure devotee of the Lord, or a Vaiṣṇava. Anyone, therefore, who becomes a Vaiṣṇava accepted by the first-class Vaiṣṇava, or uttama-adhikārī Vaiṣṇava, is already considered a brāhmaṇa, regardless of his birth or past deeds. Śrī Caitanya Mahāprabhu accepted this principle and recognized Śrīla Haridāsa Ṭhākura as the ācārya of the holy name, although Ṭhākura Haridāsa appeared in a Mohammedan family. In conclusion, Śrīla Śukadeva Gosvāmī was born a Vaiṣṇava, and, therefore, brahminism was included in him.
(Srimad Bhagavatam----1:2:2----purport).

The purpose of the material creation by Brahmā is clearly described herein. Every human being should beget nice children in the womb of his wife, as a sacrifice for the purpose of worshiping the Supreme Personality of Godhead in devotional service. In the Viṣṇu Purāṇa (3.8.9) it is stated:
varṇāśramācāravatā puruṣeṇa paraḥ pumān viṣṇur ārādhyate panthā nānyat tat-toṣa-kāraṇam [Cc. Madhya 8.58]
"One can worship the Supreme Personality of Godhead, Viṣṇu, by proper discharge of the principles of varṇa and āśrama. There is no alternative to pacifying the Lord by execution of the principles of the varṇāśrama system."
Viṣṇu worship is the ultimate aim of human life. Those who take the license of married life for sense enjoyment must also take the responsibility to satisfy the Supreme Personality of Godhead, Viṣṇu, and the first stepping-stone is the varṇāśrama-dharma system. Varṇāśrama-dharma is the systematic institution for advancing in worship of Viṣṇu. However, if one directly engages in the process of devotional service to the Supreme Personality of Godhead, it may not be necessary to undergo the disciplinary system of varṇāśrama-dharma. The other sons of Brahmā, the Kumāras, directly engaged in devotional service, and thus they had no need to execute the principles of varṇāśrama-dharma.
(Srimad Bhagavatam----3:13:11----purport).

Materialistic activities are regulated by the institution of varṇāśrama-dharma. Without varṇāśrama-dharma, materialistic activities constitute animal life. Yet even in human life, while observing the principles of varṇa and āśrama-brāhmaṇa, kṣatriya, vaiśya, śūdra, brahmacarya, gṛhastha, vānaprastha and sannyāsa—one must ultimately accept sannyāsa, the renounced order, for only by the renounced order can one be situated in brahma-sukha, or transcendental bliss. In brahma-sukha one is no longer attracted by lusty desires. Indeed, when one is no longer disturbed, especially by lusty desires for sexual indulgence, he is fit to become a sannyāsī. Otherwise, one should not accept the sannyāsa order. If one accepts sannyāsa at an immature stage, there is every possibility of his being attracted by women and lusty desires and thus again becoming a so-called gṛhastha or a victim of women. Such a person is most shameless, and he is called vāntāśī, or one who eats that which he has already vomited. He certainly leads a condemned life. In our Kṛṣṇa consciousness movement it is advised, therefore, that the sannyāsīs and brahmacārīs keep strictly aloof from the association of women so that there will be no chance of their falling down again as victims of lusty desires.
(Srimad Bhagavatam----7:15:36----purport).

Human society all over the world is divided into four castes and four orders of life. The four castes are the intelligent caste, the martial caste, the productive caste and the laborer caste. These castes are classified in terms of one's work and qualification and not by birth. Then again there are four orders of life, namely the student life, the householder's life, the retired and the devotional life. In the best interest of human society there must be such divisions of life, otherwise no social institution can grow in a healthy state. And in each and every one of the abovementioned divisions of life, the aim must be to please the supreme authority of the Personality of Godhead. This institutional function of human society is known as the system ofvarṇāśrama-dharma, which is quite natural for the civilized life. The varṇāśrama institution is constructed to enable one to realize the Absolute Truth. It is not for artificial domination of one division over another. When the aim of life, i.e., realization of the Absolute Truth, is missed by too much attachment for indriya-prīti, or sense gratification, as already discussed hereinbefore, the institution of the varṇāśrama is utilized by selfish men to pose an artificial predominance over the weaker section. In the Kali-yuga, or in the age of quarrel, this artificial predominance is already current, but the saner section of the people know it well that the divisions of castes and orders of life are meant for smooth social intercourse and high-thinking self-realization and not for any other purpose.
Herein the statement of Bhāgavatam is that the highest aim of life or the highest perfection of the institution of the varṇāśrama-dharma is to cooperate jointly for the satisfaction of the Supreme Lord. This is also confirmed in the Bhagavad-gītā (4.13).
(Srimad Bhagavatam----1:2:13----purport).

Death is nothing but sleeping for a few months in order to develop another term of bodily encagement, which we are awarded by the law of nature according to our aspiration. Therefore, one has only to change the aspiration during the course of this present body, and for this there is need of training in the current duration of human life. This training can be begun at any stage of life, or even a few seconds before death, but the usual procedure is for one to get the training from very early life, from the stage of brahmacarya, and gradually progress to the gṛhastha, vānaprastha and sannyāsa orders of life. The institution which gives such training is called varṇāśrama-dharma, or the system of sanātana-dharma, the best procedure for making the human life perfect.
(Srimad Bhagavatam----2:1:15----purport).