Maharaja Dhrtarastra accepted the order of vanaprastha, and at this stage the wife is allowed to remain as a voluntary servitor, but in the sannyasa stage no wife can stay with her former husband
SB Canto 1
The gentle and chaste Gāndhārī, who was the daughter of King Subala of Kandahar (or Gāndhāra), followed her husband, seeing that he was going to the Himalaya Mountains, which are the delight of those who have accepted the staff of the renounced order like fighters who have accepted a good lashing from the enemy.
Saubalinī, or Gāndhārī, daughter of King Subala and wife of King Dhṛtarāṣṭra, was ideal as a wife devoted to her husband. The Vedic civilization especially prepares chaste and devoted wives, of whom Gāndhārī is one amongst many mentioned in history. Lakṣmījī Sītādevī was also a daughter of a great king, but she followed her husband, Lord Rāmacandra, into the forest. Similarly, as a woman Gāndhārī could have remained at home or at her father's house, but as a chaste and gentle lady she followed her husband without consideration. Instructions for the renounced order of life were imparted to Dhṛtarāṣṭra by Vidura, and Gāndhārī was by the side of her husband. But he did not ask her to follow him because he was at that time fully determined, like a great warrior who faces all kinds of dangers in the battlefield. He was no longer attracted to so-called wife or relatives, and he decided to start alone, but as a chaste lady Gāndhārī decided to follow her husband till the last moment. Mahārāja Dhṛtarāṣṭra accepted the order of vānaprastha, and at this stage the wife is allowed to remain as a voluntary servitor, but in the sannyāsa stage no wife can stay with her former husband. A sannyāsī is considered to be a dead man civilly, and therefore the wife becomes a civil widow without connection with her former husband. Mahārāja Dhṛtarāṣṭra did not deny his faithful wife, and she followed her husband at her own risk.
The sannyāsīs accept a rod as the sign of the renounced order of life. There are two types of sannyāsīs. Those who follow the Māyāvādī philosophy, headed by Śrīpāda Śaṅkarācārya, accept only one rod (eka-daṇḍa), but those who follow the Vaiṣṇavite philosophy accept three combined rods (tri-daṇḍa). The Māyāvādī sannyāsīs are ekadaṇḍi-svāmīs, whereas the Vaiṣṇava sannyāsīs are known as tridaṇḍi-svāmīs, or more distinctly, tridaṇḍi-gosvāmīs, in order to be distinguished from the Māyāvādī philosophers. The ekadaṇḍi-svāmīs are mostly fond of the Himalayas, but the Vaiṣṇava sannyāsīs are fond of Vṛndāvana and Purī. The Vaiṣṇava sannyāsīs are narottamas, whereas the Māyāvādī sannyāsīs are dhīras. Mahārāja Dhṛtarāṣṭra was advised to follow the dhīras because at that stage it was difficult for him to become a narottama.