I am currently in discussion with a brother in my congregation regarding attendance at the second service. If time permits and hopefully you have some free, could you send on to me a brief summary as to why the Reformed Church has one.
Historically, the 2nd service was a teaching service. Hence, the catechism. In the 1st service, the minister proclaimed the gospel, narrowly, from a specific text; in the 2nd service, he taught the whole counsel of God by way of the summary of doctrine. A good reason to attend the 2nd service as well as the 1st (besides the fact that the elders, in the Name of Christ, call the congregation together) is for the sake of receiving this good balance of both proclamation and instruction.