It wouldn't ever replace ERB anyway. HAML makes most things easier and terser at the cost of making a few things difficult or impossible. You still need to fall

It wouldn't ever replace ERB anyway. HAML makes most things easier and terser at the cost of making a few things difficult or impossible. You still need to fall back to ERB occasionally, and it's also used outside of the views. All this makes for a bad default, especially for new users. (I say this as someone who loves HAML and uses it almost exclusively).