Because Prthu Maharaja's wife (Arci) was the Queen and also a daughter of a king, she never experienced walking on the ground, for queens used to never come out of the palace
SB Canto 4
The Queen, the wife of Pṛthu Mahārāja, whose name was Arci, followed her husband into the forest. Since she was a queen, her body was very delicate. Although she did not deserve to live in the forest, she voluntarily touched her lotus feet to the ground.
Because Pṛthu Mahārāja's wife was the Queen and also a daughter of a king, she never experienced walking on the ground, for queens used to never come out of the palace. They certainly never went to the forests and tolerated all the difficulties of living in the wilderness. In Vedic civilization there are hundreds of similar examples of such renunciation on the part of queens and dedication to the husband. The goddess of fortune mother Sītā followed her husband, Rāmacandra, when He went to the forest. Lord Rāmacandra went to the forest in compliance with the order of His father, Mahārāja Daśaratha, but mother Sītā was not so ordered. Nonetheless, she voluntarily accepted the path of her husband. Similarly, Gāndhārī, the wife of King Dhṛtarāṣṭra, also followed her husband into the forest. Being the wives of great personalities like Pṛthu, Lord Rāmacandra and Dhṛtarāṣṭra, these were ideal chaste women. Such queens also instructed the general people by showing them how to become a chaste wife and follow the husband in every stage of life. When the husband is king, she sits beside him as the queen, and when he goes to the forest, she also follows, despite having to tolerate all kinds of difficulties in living in the forest. Therefore it is said here (atad-arhā) that although she did not want to touch her feet to the ground, she nonetheless accepted all difficulties when she went to the forest with her husband.