Question - EPS vs PDF

Ever notice how you can save an illustrator file as a PDF or an EPS, and they look the same, but the PDF’s file size will be less than a 1 Mb, while the EPS is close to 5 Mb? I understand that the EPS embeds fonts, images, etc, but in this case the file is all paths and there’s still a huge difference in file sizes. Does anyone know why? It’s just something I’ve been curious about for a long time.