The purpose of the Udhiyah is that the rich Muslim expresses his gratitude to Allah the Almighty for His various graces, among which is guidance, and being alive till Eid Al Adha year after year.

((The best of you is the one who lived long and performed good deeds))

 Safety (not having intractable diseases), good health, and sustenance in abundance are also among the graces we should be thankful for.
 Moreover, Udhiyah is an atonement from sins that were committed and it is a treat for the family of the person who is slaughtering the Udhiyah and his relatives, friends, neighbors, and poor Muslims.