There could be a lot of reasons, like some women were intimidated before they even started, or some started to play guitar but were discouraged from playing more. Also very possible that with two equally good bands, one of all women and one with just a woman on bass, that the mostly male group could have an easier time getting gigs and had an easier time growing in popularity and success.
I’ve seen and heard comments from guys about how St. Vincent isn’t that great at guitar, not just that she’s not to their taste but sounding confused how anyone could think she was great. I’m sure that’s a minority of men saying things like that, but if she gets those comments, I’m sure women starting out on the guitar get a lot worse.
WordMan’s theory about why women are more often the bass players rather than being equally in other roles makes sense.
I wondered if being a bassist yourself might have made you more aware of bass players.
We’ve had threads before (here, here about female band members. I’m not sure whether there are more bassists than guitarists and drummers listed (though not all the women listed are “well-known”).
I was friends with a girl in high school who played drums for some local garage bands. She later got a four year degree in music and moved to Boston. She is now the drummer for an all-female Judas Priest tribute band. Hereare a couple of her drum solos.
She’s kind of a prodigy, it seems to me. She was somewhere between 13 and 16 when she recorded many of these. When she plays drums, she actually seems to take on the body movements of the original drummer.
Two great old-time blues guitarists were Libba Cotten and Memphis Minnie. The latter was a pioneer of single-string lead guitar, which was enabled by the louder resophonic guitars she played before electric guitars were commonly available.
Different instruments do seem to attract/require/favour different personalities. It’s partly tradition, but also partly true. It’s partly reasonable that guitarists have an “egotistical show-off” reputation, and fewer women cultivate that side.