I don't think it matters really if the film had or didn't have women. It's a prison movie so you kind of expect it not to have women in it anyways unless they come to visit the inmates or it's an all female "women behind bars" movie.

There's been plenty of war films where women never even factored in and it didn't make them bad. There's also been a lot of action flicks as well hwere there's no women. However there are the ones where the girls just tag along and are made to get in the way and look pretty.
So I guess what I'm saying is is that there was really no place for any women in this story. It was a male prison so of course there would be no women in it. I suppose the warden could have been a women but how would that have affected the story? And were there actually female wardens back then? I suppose we could have seen Frank's wife (let's say he had one) show up and tell him how much she misses him but we got that already from Butts and English.
There have been quite a few Eastwood movies that haven't featured women predominately.
Dirty Harry comes to mind. Yes there was Chico's wife but she never had a big role. The lack of women in that film didn't stop me from enjoying it.