When even mobile browsers have JavaScript, is it really necessary to consider potential script-free users?
It is relevant and it will be relevant even after 10-20 years when javascript might be supported everywhere. making things work without javascript is important development technique because it forces you to keep things simple and declarative
. ideally javascript should be used only to enhance experience but your website shouldn't depend on it.
there is clear advantage from maintenance point of view to have most of the code in declarative format (html+css) and as little as possible in imperative (javascript).