Luke 15:31 And he said unto him, Son, thou art ever with me, and all that I have is thine.
The father reminded his older, faithful son that he never left and everything was his. He worked for it. He also reminded to celebrate that his brother returned home.
Luke 15:32 It was meet that we should make merry, and be glad: for this thy brother was dead, and is alive again; and was lost, and is found.
Before this parable are two other parables talking about rejoicing when the lost are found. If a person is never lost, they never need to be found. Rejoice in finding those that are lost.