I like the fact I can mix PHP and HTML together. Pseudo templating languages like Twig are nice, but implementing something like Twig or even Smarty would be pretty damaging to the Wordpress community considering it's always been PHP/HTML since the beginning and to be honest, there's hardly any advantage other than cleaner code. I'd rather the Wordpress developers spend their time removing legacy code and changing some of the procedural spaghetti into nice object oriented code and adding in cool new API hooks.