The rendering engine is a non trivial portion of what Mozilla is. To be an advocate of the web user in standards discussions involving things like HTML5 and ECM

The rendering engine is a non trivial portion of what Mozilla is. To be an advocate of the web user in standards discussions involving things like HTML5 and ECMAScript. If they do not have a large enough market share of web users on their engines, they will loose their voice in those discussions. When you use a browser on the web, you are literally voting for who gets the most control of those discussions.