Not saying it's right, but that's not uncommon. Some guys inhibit because they like to fly low in the terrain and they get tired of the frequent warnings. Some guys inhibit because erroneous warnings are not too uncommon. I've experienced warnings when I was nowhere near terrain, and I developed the opinion that the TAWS was not a reliable device. I've received clear messages from mechanics to not squawk the TAWS because they couldn't fix the problem. Again, not saying that's right.
Oh, I'm veeeery familiar with the common practices regarding TAWS/EGPWS usage in Alaska 135 ops. Let's talk about a few key points.
-accuracy and reliability. Highly dependent on the hardware and accompanying database. I've not personally seen outright false hits, but I've generally operated with a little bit better equipment than the KGP560 commonly used in 'Vans.
-nuisance alerts in normal ops. Here's where I think the thinking needs to change. Yeah, there are a couple places we go that you have to have it inhibited no matter how carefully you fly. But outside of those spots, if the route/weather you're on/in is giving you "nuisance" alerts, maybe it's time re-evaluate what you're doing. If the weather is good, what are you doing so low, and if the weather is bad, well, the equipment is doing its damn job.
Lemme tell ya, I did 4+ years of flying without turning the inhibit off. But at some point, after the 4th or 5th 135 fatal where actually using the shiz that the Feds require to be in the airplane might have kept the last hole in the cheese from lining up, my thinking started to change and I've pretty close to come 180° where I leave it on all the time, VFR or IFR. It's hard to explain but when you see the NTSB photos of the exact same toggle switch locked in the INHIBIT position after a CFIT it starts to have an impact on your thinking.
Again, no judgment on this crash, gotta wait for the NTSB, but the whole thing just seems really familiar after 7 years in this business up here.