I watch them because I feel like I get a better feel for new features, their usage, and their potential, from the way Apple presents them vs reading about them

I watch them because I feel like I get a better feel for new features, their usage, and their potential, from the way Apple presents them vs reading about them in the news afterwards. For example, the new ultra wide lens. I know mentally what wide-angle lenses do, but I learned a lot from seeing the kinds of pictures they took, and the comparison between wide/normal/zoom. It was instructive to see how the Camera app uses the vertical letterboxes to show the extra content you would see if you switched to the ultra wide. I probably will not get the Pro phone, and may keep my Xr for another year. But the ~6 hrs/yr of Apple keynotes are a very information-dense way to consume a year of Apple releases, even despite the fluffier parts and AR game demos. Your question is like asking why people would ever watch a movie trailer for free - if there's something new that you want to learn about, watching promotional material is a good way to go about it.