We are used to it, down on the border, and they don't fly all of the time here. AV gas is expensive. Most are relatively high up. They keep us safe, watch our borders and sound like mosquitos. We have Border Patrol Helicopters for low observance and chases, and we see them all of the time too. It used to piss me off, its like living in a war zone, but now we need them HERE. The results are showing in positive ways.
The world is changing, its no longer the peaceful outback here it used to be. I'm not so sure the interior of the USA needs such observing robots, and I can see how everyone north of here is a bit rattled by drones. And really, they don't have the $$ to do much more than business, they (the government) don't give a hoot about hikers or outdoor enthusiasts. The one you heard/saw may be private and airspace rules do apply. Especially if it was a MOA area or wilderness. Sorry your hike was disturbed. Now the Air Force Jets strafing us in wilderness areas, that's another thing. Ear splitting engines around you when one has climbed for days to a peak are just obnoxious.
Besides, we have other invasive stuff that's more upsetting than drones...wait till they put sensors on every trail YOU hike on...they started doing that here in the 1990's, now you can't take a poop without them knowing.....