Comment by funcantor

From the blog that another reply linked (https://acko.net/blog/zero-to-sixty-in-one-second/) 'Rather than try and emulate some of the bling for CSS 3D-only environments, it's all or nothing. Without WebGL, you get plain images.' Although this blog post is from 2013, so who knows if this is the actual reason. Thankfully, the blog post also links to a video so you can still view it: https://www.youtube.com/watch?v=zjwA1VmuPnw