I'm not bashing against Haml, all that I'm saying is that is not necessary. Lately Slim also has become quite popular, so that would involve also having the Slim version. And in the future it will be something different, but as long as HTML remains as the lingua franca of the web, then there's no really need.

I used Haml in the past, and I understand it's popular nowadays mostly because of Rails, but I hardly think it's widely-used. Just to name a few that use HTML or a template engine of their own: Blogspot, Tumblr and Wordpress, and these are much more widely-used than Haml.