It's a small total count (76 in crews of 4) in a sport without a well-defined path for women and girls. It takes a long time to advance and people can hold spots for quite a while. That doesn't make for a very conducive environment for change, even if the league encourages it on the surface.
Tack on to that the fact that a certain crowd will absolutely lose their shit and harass any women in the role. Don't make it super attractive as a job.