In the centre of my radio stack is a GPS and in the aircraft flight manual it states that it is approved for IFR area navigation and N.P. IFR aproaches.............................Why would I not use it?
Basically because the user interfaces on all these devices are complete pants, so it's a question of "is it worth my while fiddling with all the knobs and buttons"? For some flights I decide it is, for others I decide it isn't.
So ... if I'm flying around the local area I might have a map on my lap, but I don't necessarily look at it. And that's about it for nav. NDB when it's time to go home, if the visibility is bad.
Further afield I might draw lines on the map, and then navigate using VORs and NDBs, which are vastly easier to programme than any GPS I've ever seen. I may or may not bother to switch the GPS on.
If I'm going somewhere I've never been before and the nav looks "interesting" then I will draw the lines on the map, navigate using VORs and NDBs, and turn on the GPS and programme the route into it and use it to check that I'm going where I intended.
But I don't do the whole hairy chested thing. I have to admit that if I've got both a DME and GPS counting down to the next turning point I don't bother to update ETAs and such on the paper plan.