Ideally we want people to actually know something about the theology and morality of being a Christian when we baptise them. If I am wrong on this next point feel free to correct me, but all those who were baptized into the Church in Acts were Jews or were gentiles who lived in a Jewish context. They thus had knowledge of what it meant to confess Christ as Lord in the Jewish faith as well as a familiar moral framework.
When Christianity came to dominate and encounter people who had no context at all for understanding what it meant to be Christian, the idea of baptizing them simply on their verbal acceptance of Christ as Lord immediately, without them getting to understand the impact of those words seems like it's rushing things just a bit. If you were from a pagan context, worshiped many gods and your religion didn't extend beyond the simple honoring of these deities, what you were entering into as a Christian does not seem clear. It was not an unwise policy to initiate people, to give them a basic understanding of just what their baptism meant. Just what it meant to consider Christ as truly Lord of your life, to die and live in him.
I would go so far as to argue that in today's western world, where a lot of millennials have no clue as to what Christianity is or means that the process of catechizing them and letting them understand what it means to become a Christian will make for converts more dedicated to the faith. This is obviously different from the Apostolic practice but for obvious reason since we are not in their context. This doesn't seem like an unreasonable accounting for delaying baptizing and why it happened later in the church's history.
