He revealed his son's identity to this assembly and declared that his son would now own and manage the entire estate. The son was overwhelmed with joy to hear this great fortune and surprised to learn that he was the rich man's son. Not only had he never had such wealth, he had never even thought of having such wealth. The assembled beings then explained to the Buddha that he was like the rich father, and they were like the Buddha's sons. Because of all the delusions and attachments and fears of life, many beings cling to lesser doctrines, thinking themselves too lowly for high attainments.
Many beings seek nirvana and feel satisfied having attained it.
They do not realize that the incredible wealth of knowledge of enlightenment and buddhahood are available to them. The Buddha sees our sad condition and offers us the hope of nirvana as an expedient means. Later he reveals the Great Vehicle, something so rich that it previously seemed a frighteningly lofty goal. Nirvana is the highest goal of Theravada Buddhism. But beyond avoiding harm to others and ending one's own suffering, there is a whole other path - The Great Vehicle.