Why isn\'t jQuery intergrated into browsers, so there would be no need to have to reference it on your site, and instead, the browser just notices the jQuery used, and every
First, there's nothing special about JQuery - it's just a more human-friendly way to code JavaScript. It takes care of more cross-browser quirks, etc. so the developer doesn't have to think about it so much.
That being said, JQuery follows ECMAScript standards, and so do browsers. IE is a stubborn one because it uses proprietary JScript not JavaScript.
The browser shouldn't handle that burdon. Do you really want to go back to the days of bloated browsers that hog 500+mb of ram and take 10 seconds to open?
On a final note, if Mozilla and Webkit just started including JQuery, it would probably piss off a lot of talented JavaScript devs who use Mootools, YUI, Dojo, etc.