What's up with that?
I call them Phantom Brakers.
There is clearly nothing in front of them yet there they are stepping on the brake. No reason.
I have a friend like that. He has to be pushing the gas or the brake at all times or else he feels like he's "not in control".
...and he wonders why his brakes only last 15-20,000 miles.

I don't think there is much of anything wrong with compression braking, especially on trucks -- and even more so if they have larger than typical tires. Works great on my truck; I've never changed the brake pads on the 1/2 ton axles since I put them in, and it slows the vehicle down nicely. There's a reason truckers do it, I suppose.

My car, on the other hand, doesn't have the compression to effectively slow the vehicle down, so I can't on it.