"The only people I know still using standalone GPS are over 65 years old. So if by "different client base" you mean, people who bought GPS in their forties and are now retired, then I suppose yes.
I think I know one other person, but it's a hand-held device for geocaching, so not exactly a turn-by-turn navigation system."
And now you know of two. I'm under 60, did not buy the GPS in my forties, and am not retired. Oh, and mine is a turn-by-turn navigation system.
I'll grant you that I bought it a few years ago when smartphones were newer, and I was trying to save money by ridding myself of the data plan. Also I liked the fact that it doesn't depend on having a live connection, which detail has been discussed elsewhere. (Though I'll add that not depending on a live connection also means not using up bits on my data plan. That data plan keeps cropping up.) Losing the data plan didn't work out, but I don't regret the purchase. When I need to navigate, I pull out the Garmin rather than my phone.
I'll also grant you that I'm in my late 50s. So maybe to you I'm just an old guy who never learned how to use one o' dem fancy newfangled "com-pooter" doohickeys.
But I think your statistics are suspect. If ground-based* GPS navigation units are as passe as you seem to think, then why are companies like Garmin and Tomtom and Magellan still in business selling them? And I see at least three more brands I never heard of on Amazon.
Still, could be you're right. Could be just us clueless old farts.
*As opposed to, say, aviation GPS.