I don't think they really trust the strap holding their tree stand on. Most people do wear a safety harness.
Yes and no
I feel based on my experience that a significant % of hunters trust their stands attachment systems for at least some of thier hunts and admittedly not often but at least for small portions of thier time on stand.
My best guess us 65-70% of the people I know who hunt out of elevated tree stands wear a FAS of some type MOST but not all of the time how often they don't I'm not sure but by their own admission its more than 1x a season
Also based on my asking about 30% of my friends and at least some other hunters I've asked do not use a safety line along with a linemans while ascending and descending from their tree stands and I asked if that means that for the moment when the risk of falling is greatest when you transition from your climbing system to thier stand thay aren't tied off as they have no safety rope so they must be on stand to attach thier FAS to the tree most avoided answering me directly yes or no.
It is only my opinion but I feel the only reason there aren't far more falls from treestands every year is nothing more than blind dumb luck. As at least half the people I have spoken to over the last 5 maybe 7 years admitted to me that forgetting to bring thier FAS/FBS wouldn't stop them from hunting which to me indicates at least sometimes they hunt without a FAS of and kind.
I once hunted without any FAS of any kind then 27 or 28 years ago I had what was best described as an "Significant Emotional Event" while climbing a huge multi trunked shag bark hickory and I exaggerate not one sintilla it was a small miracle I emerged from that "Event" with nothing more than the worst bunch of scratches in my life and a few slivers. Once on the ground the reality of the bullet I just dodged set in
I would have fallen over 20 feet hit several stout branches on my way down
It had been a very cold the last two weeks and the top few inches of ground was frozen as hard as a packed gravel road
The high of that day wasn't even above 30* and the low that night was going to be in the high teens
Cell phones weren't a factor then so I had no way to summon help
I was well over a mile in any direction from any home
I was single and hunting alone no one knew where I was or even how to find me
No one would've noticed I had failed to return to my motel room
I had no ability with me to start a fire
In short if after the fall if my injuries were bad enough and odds are they more likely than not they would've been and I couldn't get back to my truck my odds of survival were at best VERY grim.
I no longer hunt without a FAS
3-4 years ago transitioned from a FBH to a REI rock climbing harness that serves also as my linemans attachment
I have gone so far as to buy my friends who hunt really good Hunters Safety Systems FBH's and most tell me they wear them but sadly a few do not sighting they use climbing stands or ladder stands and don't need a FBH.
I can only pray the odds don't one day catch up with them