Terry,
You'd be right in most cases, but I know of three instances just this season where a stand broke free of the tree, and was no longer there to crawl back up on... Then, if you don't have a way of safely reaching the ground, you are in trouble!
We are protecting ourselves from low-percentage but high-danger situations with our fall restraint systems.
You are covering a LOT of the danger with the way you are using your system. For a variety of reasons (health, age, previous experiences, etc), some are trying to cover a few more bases. That's the idea behind being prepared with a belay system, CDS safety harness, or something of that nature.
Bill- if Jeanne wasn't such a good cook, it wouldn't be so hard to find "suitable" equipment!
Congrats on the bargain you tracked down!