I'll try to keep this brief. I know of two men who fell out of tree stands. Both werre severely injured. Neither was killed. One was partially paralized for years and never fully recoveded his upper body strength. The other was in a wheel chair for months and will walk with a limp for the remainder of his days. Both falls were completely avoidable and neither was using a harness.
My No. 1 , life long hunting-fishing buddy fell from 20' up when the straps on his
hang-on failed. He was wearing a HSS safety. It saved him from serious injury or maybe worse. He was able to easily swing to his stick ladder and come down.
I 100% of the time wear a harness (HSS Brand) when climbing. I stay attached to the tree or a safety rope until I am back on the ground. I know some don't think that such is necessary, but in my book it is.