Why Bother to Catechize?

I was going over some questions and answers to the Smaller Catechism the other day with the children and we happened to be studying one of the questions that deals with the Lord's Table. It reminded me that one of the points of catechizing was to prepare people for the Lord's Table. The job of elders is to fence the Table to keep out the scandalous AND the ignorant. Why? So that they don't eat or drink judgement unto themselves. Communion has a serious negative sanction attached to it. Catechisms were then formulated as a way of instructing people so that they would be able to discern the Lord's Body before they partake of it.