Why Fewer References to Holy Spirit vs. Father and Son?

Let’s consider the New Testament and particularly the gospels, since the Son and the Holy Spirit were not as clearly manifest in Old Testament times.

In the gospels, the Son is made clearly manifest through the Incarnation (John 1:1-3, 14). Jesus is the focus of the Gospels, as is also his relationship to the Father, so that explains why the Holy Spirit is not mentioned as much in the Gospels. His role in the New Covenant era was not yet clear. Yet, we know that Jesus promises to send the Holy Spirit to aid his Church (John 16:13), and so the Holy Spirit becomes more prominent in the Acts of the Apostles and the various other New Testament books.