There's several reasons, read this post and Brendan's corresponding comments about it: https://news.ycombinator.com/item?id=4630057 https://news.ycombinator.com

There's several reasons, read this post and Brendan's corresponding comments about it: https://news.ycombinator.com/item?id=4630057 https://news.ycombinator.com/item?id=4630057 Practically speaking, it's quite a large engineering effort, duplicates maintenance work, and introduces a whole host of new problems (backwards compatibility, etc) itself. Not to mention the politics involved in getting all the browsers on-board and agreeing to a whole new completely different standard.