It's an age thing partly: leftovers of history The US had a *very* high level of offical institutionalized sexism right up until 1972, when the Supreme Court ruled that job advertisements weren't allowed to be ***-segregated. Anyone who grew up before 1972 was in a culture absolutely *mired* in sexism, where it was routine to advertise jobs to "men only".
And we generally appoint older people to the upper levels of organizations.
There are more female railroaders *now*. But Joe Boardman was born in 1948, and in that age bracket there are very very few.
There's still institutional sexism now, of course, and it's still a serious problem, but it was really really bad before the 1970s.