Several of the stories published so far hit on something really crucial, I think, which is that as a ringer, and particularly as a visiting
ringer, one is often asked to publicly assess one's own ability to do something: "What bell would you like?" or "Could you call this?" or "How's your Stedman?" We've seen that women often are not asked these questions at all, but even when they do get asked, questions like these can mean different things to different people. Personally, when I've been asked "What bell would you like?", I've considered all of the following possible nuances of the question before responding:

1. "What bell are you confident you could ring well?"
2. "Where do you think I should place you for optimal striking across the band?"
3. "What bell would you be willing to ring that you don't think anyone else especially wants to ring?"
4. "What bell would you like more practice on?"
5. "What bell have you always secretly wanted to have a go on?"

Combine all these considerations with the fact that whatever mistakes you make will be audible across town, and you've got a recipe for a lot of polite, deferential, self-deprecating people asking to ring the 6 of 12--or refusing to call a touch, knowing that someone else in the band could do a better job.

I don't know how best to build a safer environment for making mistakes. One thing might be for tower captains to be more precise in their language--make clear when you're offering an opportunity to practice something tricky, versus when you'd like the striking to be really good, and make sure t provide plenty of opportunities for both. (Simulator practices are great for this.) And, of course, if you're asking a visitor, provide information about the bells so that the visitor feels more confident in assessing their own ability. Another small thing I like is when a tower captain says, after a touch has fired out or someone has done some bad striking, "We'll have another go at that later." This makes clear that you're not upset that someone made a mistake, and you're willing to provide additional opportunities for practice. I also really appreciate when tower captains keep track of who's been placed where throughout the practice, and then use that information to ensure that no one is overly typecast (unless they really want to be). For conducting, it can be helpful to ask someone to call something
and then give them a touch's worth of time to think about it (or to ask their favourite expert for advice), so they don't feel so put on the spot.

Generally though I think it's a cultural fact that women in ringing are less willing to make mistakes (including when trying to correct other people who have gone wrong). "But the women in my tower never want to conduct/ring round the back/ring anything outside their comfort zone" is not a good reason to keep asking the same four men to do all those things.