I am guessing that most are used to straightening during tempering (my preferred method), so don't have the experience with post quench straightening. It is not like post quench straightening is risk free.
I imagine many of the participants are used to heat treating known steel with thermal cycling and PID controlled ovens prior to quench in a engineered and known quenchant. Under those conditions, warps that are hard to address in tempering are uncommon. The other issue with post quench straightening is that where your window starts and stops is kind of dependant on knowing your quenchant/steel combo. Otherwise, you may hold the blade in the quench past the point of plasticity. So, I get why it isn't more common, but it may be good to practice prior to going on FIF as it doesn't seem that they let you correct issues in the temper.
On a different note, this was one of the more irritating final challenges that I have seen. The knives themselves were a terrible design (not the participants design, I mean a stupid thing with finger breaking holes and claws and crap) all things considered. Further, the strength test was abusive in a ridiculous way. The participants could have made different design decisions to make the tips of their knives into pry bars, but doing so would have made them definitely worse at stabbing people. The claws on this ridiculous knife are utterly worthless as you remove the advantage of reach that the blade and if you were to use them, they are not long enough to practically cause any incapacitating damage. As a fighting knife, this thing was crap, and to pass the strength test without bend or break would require a redesign that would make it even worse.
