http://awuuwa.i2p/webpages/why_no_javascript.html
As a standard, it is far too heavy and expensive and thus difficult to implement, to the point that it makes it next to impossible to make small independent web browsers to compete in the market. In that, you only need to just take a look at how things are, there's at most 3 different web engines that can pull off javascript, the chromium base, the firefox base and the webkit one.