Why does Augustine "interrupt" his narrative to tell his reader about Alypius and his addiction to the gladiatorial contests?

Augustine tells his reader about Alypius' and his crave for blood shed for two reasons: one to teach his church congregation, and also to highlight the struggles and problems he and his friends are experiencing when living outside of the Catholic Church. When reading Confessions one must realize Augustine's role and position as Bishop; the churchgoers would have looked up to Augustine for guidance and advice. Also, when Augustine talks of gladiatorial contests one must realize that  at this time, gladiators are linked with blood lust and the 'persecution of Christianity. Essentially the gladiatorial games signify sin. Therefore, when Augustine talks of Alypius's blood lust story perhaps he is teaching his church congregation that anyone can fall into a sin, even a man of good character (like Alypius). In addition I believe that Augustine tells the story of Alypius's addiction to the gladiatorial games to enhance the fact that Augustine and all his friends were each living in some sort of sin. In this point of the narrative, Augustine's lifestyle, Augustine's friends, and Augustine himself are all sinful; also Augustine has not yet experienced a conversion. Perhaps he focuses on this to point out he was indeed in need of a conversion. By highlighting the sins of himself and his peers he highlights the fact that true goodness and true good living cannot be reached without a sincere conversion. We see this theme (of the necessity for a conversion) often portrayed in Augustine's Confessions.