I graduated from uni with a Computer Engineering degree in 2005- ML wasn't really a thing being offered at that point. I loved algebra and calculus but hated statistics. All I hear about these days is machine learning, so I wanted to see what the fuss was all about, as I've really never been exposed to it. I also wanted a university style exposure to it as I wanted to ease into some of the statistical concepts necessary as I wasn't good at them way back when and I haven't practiced them in 10 years.
Finally, after some initial exposure, I may find that ML or some of its concepts will be another tool in my problem solving tool bag.
I feel like a lot of people have my same motivation. We are hearing all the hype, we weren't really exposed in our formative years, and we're curious. Also, my particular course was free. So what's the harm?