That is the difference between the demons and the devotees, or the worshipers of Lord Śiva and the worshipers of Lord Viṣṇu.
While Śukadeva Gosvāmī was narrating the history of Vṛkāsura, he addressed Mahārāja Parīkṣit as Bhārata, referring to King Parīkṣit's birth in a family of devotees. Mahārāja Parīkṣit was saved by Lord Kṛṣṇa while in his mother's womb. Later, he could have asked Lord Kṛṣṇa to save him again, from the curse of a brāhmaṇa, but he did not do so. The demon, however, wanted to become immortal by killing everyone with the touch of his hand. Lord Śiva could understand this, but because he had promised, he gave him the benediction.