"passion-based career choices" are 80% of the reason that women make less than men in most fields. They have a reputation as being there as a passion, not as a mercenary, and with less aggressiveness, are more likely to stay at a lower salary level if passed over for promotions, too risk-averse to leave for somewhere new.

Also they can follow their passion because many see their career as a sidelight until they marry and become mothers.. Men don't have this backstop or alternate way to follow their "passion", for men, low income = no marriage.