It has been common practice in many Christadelphian ecclesias for people wanting to be baptised to go through a lengthy period of preparation in which the "essential doctrines" are taught. Even people who have been brought up in the faith have to "go through for baptism" and finally face a public examination (sometimes called an "interview") conducted by the ecclesia's "examing brethren" before they can be baptised. It's not uncommon for the "interview" to last two or more hours, and fine points of doctrine are carefully examined.
In recent times there has been a great deal of scrutiny, and criticism, of baptisms in "mission fields", especially if there has been any suspicion that the "interviews" haven't been up to the same standards of thoroughness as in countries where Christadelphianism has had a longer history.
Consequently many Christadelphians face their baptism with fear, apprehension and nervousness about how they will do in the examination - will they remember all the proof texts? will they make an embarrassing mistake? etc. - and not with the joy and rejoicing that seemed to characterise many of the baptisms recorded in the New Testament. Christadelphian baptisms tend to be solemn rather than joyful occasions.
While baptismal interviews cover the "essential doctrines" in great detail, there is usually little emphasis on accepting Jesus Christ as a personal Saviour, or on "receiving" Christ (John 1:12). While there is usually considerable emphasis on what a believer must do after baptism in terms of their duties and responsibilities, little is made of what God will do for them.
No wonder then that many young people brought up in the Christadelphian faith are either delaying baptism or opting out altogether.