teaching - What is the point of a lecture when you have a textbook?

I never really understood the point of having a course with lectures when the course has a textbook. Sometimes the subject is so high-level or specialized or so modern that the contents are changing rapidly that there is no textbook (for example at the graduate level). But more often the textbook includes everything that will be said in the lecture, and much more: extra content, exercises, answers to exercises, appendices, etc.

I assume a STEM context, that is we can assume the textbook is available in the sense that there is one comprehensive source that contains undisputed facts, as opposed to a broad literature with lots of interpretations and opinions (as may be the case in non-STEM contexts).

So what is the point of a lecture?