The lecture format is an efficient way of presenting a number of facts and ideas to an audience in a short time frame. It is a relatively smooth process, particularly when the lecturer has prepared the material in advance. Moreover, one person can lecture a large group, which saves time. This is particularly useful in an educational setting with a large number of students relative to faculty size.
The audience for a lecture comes from different backgrounds, with differing levels of knowledge about a topic. The lecture format could lay the ground for further study of a topic by providing the audience with an introduction that puts everyone on the same footing. The lecturer could present all the basic information that the audience needs to know about the topic.
Some information is not readily available in a single format and could be spread out across different sources, such as journals and textbooks. It is convenient to present such material in the lecture format. A lecturer also could give current information in areas where the available written information is not the most current, since research is ongoing.
The lecture method provides an opportunity for an audience to get the benefit of input from experts. Someone who has some expertise in the area can provide the benefit of his expertise to the audience. This could be, for instance, someone who has conducted research or someone who has helped turn around a company. This sort of first person account helps provide the audience with first-hand information.