Just because talking to a group is not optimal for an average group member, it could still be close to optimal for some of them (the audience that the speaker had in mind when preparing the speech), and could maximize the total knowledge—as a toy model, instead of one person getting 10 points of knowledge, there are ten people getting 5, 4, 3, 3, 2, 2, 2, 1, 1, 1 points of knowledge, each number smaller than 10 but their sum 24 is greater than 10; in other words, we are not optimizing for the individual’s input, but for the speaker’s output.
But building common knowledge seems more likely. The advantage of speech is that everyone knows that everyone at the same lecture heard the same explanation; which allows later debates among the audience. If you read a book alone, you don’t know who else did.
And of course, signaling such as “this person is considered an expert (or has sufficiently high status so that everyone pretends they are an expert) by both the organizers and the audience”. I would assume that the less information people get from the lecture, the stronger the status signaling.
Just because talking to a group is not optimal for an average group member, it could still be close to optimal for some of them (the audience that the speaker had in mind when preparing the speech), and could maximize the total knowledge—as a toy model, instead of one person getting 10 points of knowledge, there are ten people getting 5, 4, 3, 3, 2, 2, 2, 1, 1, 1 points of knowledge, each number smaller than 10 but their sum 24 is greater than 10; in other words, we are not optimizing for the individual’s input, but for the speaker’s output.
But building common knowledge seems more likely. The advantage of speech is that everyone knows that everyone at the same lecture heard the same explanation; which allows later debates among the audience. If you read a book alone, you don’t know who else did.
And of course, signaling such as “this person is considered an expert (or has sufficiently high status so that everyone pretends they are an expert) by both the organizers and the audience”. I would assume that the less information people get from the lecture, the stronger the status signaling.