CBT as a kink may be an evolutionary adaptation to protect men's most vulnerable (and evolutionarily useful) body part.
I have no idea why it's out there, but I suppose abusing it a bit may help toughen it up enough to ensure you can still have children when an accident happens.
Nah, CBT is just your good old Cock and Ball Torture. I don't think there is any evolutionary advantage, source: I've never seen any other species perform it (trust me I've looked). But I do think some men pay for it rather than paying for therapy so there's that.
That' definitely not hiw evolution works. Evolution is not something you "train". If for example you wanted to make the human race more muscular in future generations sending them to the gym would NOT work, you would have to literally cull the weak yound and old to force a genetic adaptation to future offspring.
I'm not saying cbt itself is evolution, I saying the kink for it evolved. So eg. some random freaks are into cbt - they end up with tougher balls and are less likely to lose their ability to have children due to some accident - they have a few more children on average and so on... until its a regular kink to protect men's balls.