For the longest time, one of the basic technical requirements for website projects I’ve worked on was that the site should run with javascript disabled.
It actually caused a great design by-product: concerns were nicely separated between basic functionality and user-experience improvements. Beyond that, I don’t know of any reason to do so anymore.
Assuming that I’m targeting the widest user base possible, are there any reasons not to make javascript required?
If a significant fraction of your user base (real or expected) — for whatever reason — browses with JS turned off, then of course your site should work well with JS disabled.