This is a problem a lot of people have; they think in technology instead of actual problem solving. Just look at how many projects have been posted on here with a title like "$solved_problem... in Rust!" as if Rust makes everything better forever.
It's marketing bullshit. It's self-gratification. It's using a technology for technology's sake, not for solving a problem. And it's costing the industry billions in sunk cost, dead ends, overcomplicated and unmaintainable software. Because one guy felt strongly about a language or technology.
Not if you want interactivity in certain parts of the doc site, such as what Stripe does with API keys. It's simply easier to add JS if the entire toolchain is JS.