Native & bookmarked apps need launch screens in .png format. It can be quite cumbersome to make launch screens for dozens different resolutions and/or languages. On the other hand it would be very easy to implement the correct look and feel in a responsive manner.
The launchscreen-shot utility generates .png screenshots from your launchscreens for all desired resolutions.
Webfont Support for PhantomJS: http://arunoda.me/blog/phantomjs-webfonts-build.html