Modern web development emphasizes interactivity
A simple script that ran a countdown timer, for instance, would be easy to program and would add another level to your website. If your site is primarily focused on fitness, then you may want an interactive workout center that is clickable that can explain what each piece of equipment does and the exercises that go with them.
However, that is just regarding your personal experience with designing your website. The goal of any site is to eventually draw large amounts of traffic and grow exposure to solidify either an idea or a brand.
The overall benefits of using the language far outweigh any potential cons and will make you more satisfied with your site and the work you have put into it.