One explanation for this is the philosophy known as "Strong Cessationism", which attempts to explain apparent "cessation", or stopping of God's appearance (known as "theophany") and miracles.

It begins from the recognition that the Bible is complete, sufficient, and perfect. Any additional revelation from God would be unnecessary; even counterproductive to the completeness and perfection.

This is likewise connected with the sacrifice of Jesus; the sacrifice is so complete and perfect that no further divine intervention is required or desired.

Of course, nobody really knows the ways and purposes of God.