Disabling JS displays nothing at all, while changing text and background color is a progressive enhancement.
Content should still be accessible without JavaScript, even if, perhaps, in a less convenient way, i.e., every click reloads the entire page
It's the World Wide Web. Being accessible to everyone is the whole point.
We have other platforms that target specific markets. That's fine. But we only have one Web.
It's not an arbitrary rule, it's just that they always have.
That's the hole point of progressive enhancement, you don't start requiring some technology as soon as it reaches x% market share and ignore the remaining minority. You build on top and offer a better experience to those that can or want.
In the apps world, it's usual to draw a line on a set of minimum system requirements and expect that line to move forward as the years go by.
But this is the Web, being accessible should be a priority.