Because the course does not start automatically

Because so many people are watching non-work related videos at work, and getting in trouble if a video starts at a high volume, you have this problem. Google (who owns youtube) wants people to have a chance to turn their volume down and not get in trouble, yet keep watching their videos. So they made the browser so the user must interact with a web page (or series of pages) before a video can play, giving the user the opportunity to turn the volume down first. Other browsers followed them, so you can't start a video on your project until the learner has interacted with the web page - usually by clicking something. Not your fault, not Articulate's fault, it's the browser's design.