The Music Industry, Movie Studios and other companies who create media contents are always concerned with people getting access to their content without paying for it. Now the companies won’t need to rely on third-party plugins like Flash and Silverlight to deliver copy-protected movies and TV shows to your browser. Mozilla has decided to adopt DRM in HTML5 in an effort to keep Hollywood happy and to give hard competition to major web browsers, or otherwise people will just shift to those other browsers. Some organisations and individual security experts are criticizing Mozilla for choosing close-source CDM.
Source: https://thehackernews.com/2014/05/mozilla-to-enable-html5-drm-in-firefox.html