Why just HTML you ask? Well all the reasons that they provided plus the fact it's only HTML files.
This whole stack argument is silly, just let people use what ever they want to use. If someone wants to use a giant complex webpack setup, that's perfectly fine. Sure there is obvious downfalls and longer term maintenance can be a hassle, but it's what they enjoy.
If you want to use just HTML and CSS, go for it, but why are we bragging?