Turning it off is not "just totally stupid". For one thing, scripts are sometimes annoying, and most of the web can still be successfully navigated without bothering with them. Turning scripts off can greatly decrease site load times, browser overhead, and network traffic.

For another, you don't know what sort of user agent the customer is using - there are a lot of browsers for particular accessibility issues or other purposes that do not evenly support Javascript.

Supporting lack of javascript is just plain best practice, based on the principle of progressive enhancement.