Why did Jesus perform miracles? The miracles of Jesus were not random acts. Rather, they carried a specific message to the nation of Israel, those who Christ first came to.
In the New Testament the word "miracle" and the word "sign" both come from the same Greek word: semeion (say-mi-on). The meaning of the word is an explanation of something hidden and secret, denoting a sign, mark, indication, token, or wonder; and can be a warning, admonition, or instruction of truth. The key to Christ's miracles is the meaning of this word.
Jews demand miraculous signs and Greeks look for wisdom, but we preach Christ crucified: a stumbling block to Jews and foolishness to Gentiles -- 1 Corinthians 1:22
Therefore the Lord himself will give you a sign: the virgin will be with child and will give birth to a son, and will call him Immanuel. -- Isaiah 7:14
This will be a sign to you: You will find a baby wrapped in cloths and lying in a manger. -- Luke 2:12
Thirty-seven of Christ's miracles are recorded in the gospels: twenty-one of them in Matthew, three of which only appear in Matthew; nineteen of his miracles are recorded in Mark, two of which only appear in Mark; twenty-two in Luke, seven of which only appear in Luke; and eight in John, six of which only appear in that gospel.
Jesus' miracles were a sign to the nation of Israel that He was their promised and long awaited Messiah. However, in spite of all of the miracles and signs that Jesus gave to the nation of Israel and the religious rulers, they rejected their Messiah.