It is prudent to presume you live on the long side of the bell curve in exercises like this. I know that my planning horizon is very likely way beyond where I'll die, but, as mentioned many times, the discomfort associated with running out of money is much worse than the pleasure of another couple of percent.
As to the idea of alignment of facts to support a pre determined result, I agree there is a lot of that here. Some of it is cognative dissonance avoidance, since the determination has already been made and there's the need to "prove" it was the right thing to do. For instance, someone who just now took SS at 70, and is in poor health. If they'd taken it at 62 and put it in equities, they'd be way ahead... they'd have to live past 100 since the market over the last 8 years has been so profitable.