Mainly, I meant to unbundle "what" from "why." I think it is what people do that bothers you. For people who are already disappointed by "what," learning "why" might be a positive experience.

I think that people who do not know about human cognitive biases tend to hold lots of false beliefs on the "what" side, for example by employing various pieces of dark side epistemology to protect certain cherished false beliefs about human nature.

And self-knowledge is necessary for self-improvement, for you produce your own happiness.

yes but self-knowledge is not necessary for happiness - let us be clear, you might never get as much happiness back through effort as you lost through debiasing. Not that that bothers me, because I value truth very highly, but it would bother some people.