Without justifying it, the reason is simple. They are using a front end framework (bootstrap) that many developers use/understand that also supports 99.9% of browsers.

Running a browser without javascript that you still want graphics to display (so not a screenreader or text-based-browser), is part of the .1% they are willing to disappoint.

Do I think it is overkill? Sure. Do I still use jQuery at work even though the vast majority of its once handy features are now baked into JS in the browser by default? Of course.

It’ll be a run-on effect of whatever framework they are using, and they very justifiably don’t want to bother catering to you. Having JS disabled in 2026 and complaining about sites not behaving is simply a performative act.