Reasons:

• To simplify pagelayout
• Make it easier to override script / style handling
• Make it work like ezwebin

Also, this is needed by ezjscore to be able to override the JavaScriptList loading. As in be able to pack the javascript files and make sure JavaScriptList are loaded before ezscript_require() to avoid this:
http://projects.ez.no/ezjscore/forum/general/question_about_ezscript_require#msg19151

In short: Both jQuery and Yui 3.0 plugins are overwritten if you load the main library file again after the plugins are loaded, so it's crucial to make sure all scripts are loaded in the correct order. JavaScriptList are global scripts, and should therefor be loaded first.

Note: the patch also optimizes the IE conditional statements for styles (png transparency is supported in IE7 so no need for pngfix there, and IE8 is acid 2/css 2.1 compliant so no need for ie css work arounds ) .