Gender parity is more significant for medicine as there are a great many patients who have trouble working with a doctor of a particular gender. It's not always same-gender pref either - I know of two women who prefer male gynaecologists because they're less rough when examining.

Given the importance of medicine to leading a happy life, it's important to get as much information out of patients as possible - so it's in the interest of the industry to make sure that the client-facing staff have plenty of both genders.

It's much less important in programming as users and programmers rarely interact. Was Firefox written mostly by men or by women? It doesn't matter to me as I don't interact with them in order to use the service Firefox offers.