When adults are learning to read, nobody hands them a pre-primer that a young child uses in learning to read.

Neither the Baltimore Catechism nor the Catechism of the Catholic Church are the Living Word of God.  They are not Sacred Scripture.  These documents were written in their time, for people of their time.  They are not timeless documents.  These documents become obsolete.  As an example, let's look at the first Code of Canon Law of 1917 [this was the first universal code of Canon Law in the history of the Church].  And this Code only existed for less than ninety years.  

Did things change?  YES.  I mention the 1917 Code, because THAT Code unified the current system of appointing bishops.  In 1914, on the eve of World War I, 73% of the bishops of the world had NOT been appointed by the Holy See.

And that Code of Canon Law of 1917 was tried, and it didn't work---so a new Code had to come out in 1983.  And it time, probably a faster time yet, it will be obsolete, too.