There are many aspects to this question. Of his own free will God created human beings in his own image. That means we too have free will (CCC 1701-1715).
We were created to freely choose to love God (CCC 356-361). We respond in faith to the initiative of God who reveals himself (CCC 142-184). If God manifested his great power more immediately our response would be forced.
Free will also means we can choose to sin, and sin obscures God from us (CCC 1845-1853). So this world is in a state of journeying towards God but will one day arrive at full perfection when all will know and serve God (CCC 309-314).