can be used to provide progressive enhancement, an approach which
just plain old HTML without any funny looking inline script,
like adding interactivity, visual effects, or pretty much whatever you dream up
(and this is important, and many other technologies forget about it)
of accessing and navigating a site or application
There a lots of people who are not fortunate enough to have Javascript access. Some of them have disabilities, some of them have their environment controlled by where they work, others are computers, not people.
Text-only browsers have a horrid time with most sites. For example take a look at how Unobtrusify.com fares in the W3m browser
Find out more about how and why this site was built.