Because it's right.
I believe in one Lord Jesus Christ, (1 Corinthians 8:6, Ephesians 4:5)
the Only Begotten Son of God, (John 3:16)
born of the Father before all ages. (Colossians 1:15, 1:17)
God from God (John 1:1-2), Light from Light, (John 1:4, 1:9, 2 Corinthians 4:6, Hebrews 1:3)
true God from true God, (1 John 5:20)
begotten, not made (John 1:18), consubstantial with the Father (cf. 1 John 1:5 & John 1:4, 1:9);
through him all things were made (John 1:3, 1:10, Colossians 1:16, 1 Corinthians 8:6, Romans 11:36, Hebrews 1:10).
For us men and for our salvation (Matthew 1:21, 1 Thessalonians 5:9, Colossians 1:13-14)
he came down from heaven, (John 3:13, 3:31, 6:38)
and by the Holy Spirit was incarnate of the Virgin Mary (Luke 1:34-35),
and became man (John 1:14, Hebrews 2:14).
For our sake he was crucified (1 Peter 2:24) under Pontius Pilate (Mark 15:15),
he suffered death (Matthew 27:50) and was buried, (Matthew 27:59-60)
and rose again on the third day (Mark 9:31, 16:9, Acts 10:40)
in accordance with the Scriptures (Luke 24:45-46, 1 Corinthians 15:3-4).
He ascended into heaven (Acts 1:9)
and is seated at the right hand of the Father (Mark 16:19, Luke 22:69).
He will come again in glory (Mark 13:26, John 14:3, 1 Thessalonians 4:17)
to judge the living and the dead (Matthew 16:27, 2 Corinthians 5:10, 2 Timothy 4:1, 1 Peter 4:5)
and his kingdom will have no end (Hebrews 1:8, 2 Peter 1:11).
I believe in the Holy Spirit (Acts 1:8), the Lord, the giver of life, (John 6:63, 2 Corinthians 3:6)
who proceeds from the Father (John 15:26) and the Son (John 16:7),
who with the Father and the Son is adored and glorified, (2 Corinthians 3:8)
who has spoken through the prophets (1 Peter 1:10-11, Ephesians 3:5).
I believe in one (Ephesians 4:4), holy (Ephesians 1:4, 5:27), catholic (Matthew 28:19, Acts 1:8) and apostolic (Ephesians 2:20) Church (Matthew 16:18, Romans 12:4-5, 1 Corinthians 10:17).
I confess one baptism (Ephesians 4:5, Galatians 3:27, 1 Corinthians 12:13) for the forgiveness of sins (Colossians 2:12-13, Acts 22:16)
and I look forward to the resurrection of the dead (Romans 6:4-5, 1 Thessalonians 4:16)
and the life of the world to come (2 Peter 3:13, Revelation 21:1). Amen.