Inconsistency across browsers was one of the things that inspired the development of the various js libraries we use today, including jQuery. Despite the exist

Inconsistency across browsers was one of the things that inspired the development of the various js libraries we use today, including jQuery. Despite the existence of standards (even standards with comprehensive test cases), they are needed to abstract away the differences between the IE, Firefox, Safari etc DOMs. If browsers were to embed a native implementation of jQuery, you'd then have to have some kind of meta-jQuery library to abstract away the differences between IE jQuery, Safari jQuery and Firefox jQuery (etc).