When even mobile browsers have JavaScript, is it really necessary to consider potential script-free users?
Yes, it's relevant. Mobile browsers in use today do not all have Javascript enabled. It's available on new phones, sure. But there are millions and millions of people like me, who have phones running older browsers, and for all of us, a JS-required browsing experience is just plain broken.
I don't even bother visiting sites that didn't have progressive enhancement in mind when they coded. I'm not technically behind the times. My phone is a year old. But I'm not going to re-up my contract and buy a new phone because of a crippled web experience.