Seeing the serpent wrapped around the neck of Lord Shiva, many times you must also think that why does Shiva give him a place in his neck?
According to mythology, Nagaraja Vasuki was an ardent devotee of Lord Shiva. He was always absorbed in his devotion.
Meanwhile, the work of churning of the ocean began when Nagraj Vasuki did the rope work. On seeing his devotion, Bholenath was very happy.
He gave Vasuki the boon to keep him wrapped around his neck. In this way Nagaraj Vasuki also became immortal and started clinging to the neck of Lord Shiva.