Because women get punished for being more assertive.
There is no link between being a woman and being able to do less. What DOES happen is when men suddenly become interested in a career field, it gets gender role'd and women are pushed out.
See: women were just as interested in comp sci until the mid 80s. What happened in the 80s? Working with computers became a "boys thing" and the family computer became something you put in your son's bedroom instead of the living room. Women were then pushed out of the field. Even the girls computer camp switched over to "it's about meeting boys":
(ad is from '83)
Any other stance is willingly trying to ignore why the current state is caused by non-inherent reasons. The current state is because a bunch of men were and are still afraid that a woman getting a job or a raise means a job or money lost for a man. The status quo benefits those who win a penis in the genetic lottery and people will fall over each other trying to justify their status quo benefit for any other reason than pure chance of what they were born with between their legs.
Just imagine being bombarded with this shit just for having a vagina:
every day
every where
every moment
it becomes a mental and societal jail that becomes easier to survive by just playing along. It still fucking happens. People are still fighting against equal pay and want to destroy the Lily Ledbetter Act and any chance of an amendment to the constitution that simply states women are equal to men.