People learn things differently. Some people learn a lot better in a lecture than reading it. Also it gives you a chance to interact with the speaker and othe

People learn things differently. Some people learn a lot better in a lecture than reading it. Also it gives you a chance to interact with the speaker and other audience members at the same time and ask questions and have a discussion. It also lets the speaker tailor the talk to the audience and their questions. Both formats have their place, and often a talk is turned into exactly what you describe -- a blog post with a text description, a highlight reel, and the full talk (that you can watch at 2x speed if you really want to).