These can be broken down into software issues and policy issues. Software issues revolve around the choice of browsers. It's easy to recommend a current browser, but that may not work for the user. The browser in my PDA can't do JavaScript, but I can browse a lot of sites from it anyway. Furthermore, if JavaScript is unstable or has security bugs, in certain browsers it's effectively unavailable.
Policy issues come largely from the potential security and stability issues mentioned above.
Both individuals and companies may establish policies against the use of JavaScript, even with browsers that have support for it. Dependency vs. enhancement One of the reasons people object to JavaScript, rather than merely ignoring it, is that some Web pages require it. One of my favorite examples of this is a clever little splash page I saw recently. Because the redirection was entirely in JavaScript, and if you didn't have JavaScript, it just didn't work. A particularly annoying variation of this is to use JavaScript as the only way to follow a link.