Honesty is a by-product of valuing truth and goodness.
People raised to disregard the transcentals become sociopaths. Honesty is never introduced as a character trait along with other virtues.
In my view, this is the baseline of mental illness, a lack of virtue. Vice then feeds a broken mind. Once mental illness begins, incentives have nothing to do with human action. It is all derangement and must be identified as such.