Jesus was able to teach scripture using parables so that his followers could better understand their meaning.

With the popularity of sola scriptura, the Church can ill afford to have parishioners also start making their own interpretations. While it can be interesting to get into theological discussions, most people aren't as involved as that. Parables were able to relate the spirit of scripture rather than get lost in the detail. Similarly, if the Church is able to better explain the Gospel, people wouldn't go off reading mistaken interpretations. We mustn't presume that because most people can read these days that they are scholarly.