I think it depends on the conference, but my general impression is that mere mortals cannot expect to get speaker spots. In most cases, the organizers or at least the community in general want well-known speakers. There is no way random people are allowed to just walk up there and present. That's probably for the best, since as an organizer you want to have some kind of quality control. I do suspect that's part of the gender ratio problem though.
When I started to do open source development, I tried to speak at several OS conferences. In most cases I didn't hear back, but once they told me in no uncertain terms that they didn't tolerate "no-name" speakers (even though the signup page implied everyone was welcome).
When I started to do open source development, I tried to speak at several OS conferences. In most cases I didn't hear back, but once they told me in no uncertain terms that they didn't tolerate "no-name" speakers (even though the signup page implied everyone was welcome).