The women gamers in my experience lack the confidence to GM.
Yes, at a certain level, it's about respect. We like playing with grit and pseudo-realism, and we typically feel constrained with that if women are around. The few times a woman has played with us (had one in a long term Traveller campaign I ran) I explained to her husband first, then to her, how gritty the game can sometimes be.
It bothered her the first time a PC died with her as DM, worried she'd pressed the group too hard etc. She was fair and would listen.
I have no preference but I'd like to see female DMs more. Right now we are going to have a roleplaying event with seven male DMs and just one female DM. This simply doesn't sound right to me, especially because we have 6 female participants and 14 male participants.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.