I'd argue it's "needed" every flight. I have a full-IFR avionics suite that has never once, in the year I've been flying it so far, had the VOR portion of the Avidyne turned on to see if it even works. I'll get around to that later, if I ever start my IA training. GPS is so pervasive and convenient, the magenta line has become my 100% navigational go-to. It's a safe bet many of us here roll this way.
The most effective pushback against diddling with GPS, which is a mil / gov system we've all grown utterly dependent on in many aspects of smartphone life, will come from soccer moms trying to navigate somewhere on the southern SC seaboard in their Lincoln SUV's when Siri can't get a sat lock while the fleet trains offshore. Their protests will be heard. And then ignored. "Nav for me but not for thee, peasant. Pick up that can!"