For a very long time the web was static. It was plain text, some images, and not much else. We could do some great things with just text and images, but ultimately it wasn't that exciting and developers wanted more. So browsers added JavaScript, and CSS, and a few other things that have fallen away now like Flash, and life was pretty exciting.
But with developers being who we are that wasn't enough.
Then came WebGL.
And developers mostly ignored it because it's really, really hard.