However, looking back, I'll admit that what you've written above probably had alot to do with it. Having never seen or read many (at that point) strong, interesting, multidimensional female characters, they were harder for me to imagine or play. Whereas, playing males definitely opened up those possibilities.
That sounds familiar! For a few years when I was a teenager I'd deliberately plot my female characters as male in an attempt to get out of the stereotypical ruts. I've also read a rant by an agent who sometimes wants to tell writers to make sure their story wouldn't be more interesting if they switched everyone's gender, which has always sounded like a good exercise to me. I find when I imagine that, I notice automatic assumptions I hadn't even realised I was making.
I'd love to see more of that.
Somehow, I wonder if some of the use/tendency towards asexual characters doesn't stem from this in part. The desire to make a female character but having less to go on.
This isn't to say all, but I wonder if it's not a percentage of it.