I am finding this hard to believe, honestly. I am curious if you mean books or comics or …?
The default character is male. Usually a white, straight, cisgender male (in America). We seem to think that everyone can identify with this character and have been conditioned to think as such for a very long time. There have been so many kinds of male leads that we think this character is versatile. The roles women fill have not yet shown many of us that women are just as versatile. The idea that women aren't as "cool" or "interesting" (have heard this!) as male leads is a misconception that I think a lot of people are trying to erase precisely by having female leads that break the molds of what women are supposed to be like. Think about some of the somewhat recent TV shows popping up with prominent female support characters or even female leads -- Continuum, the 100, etc.
Books, shows, games, movies, etc with female leads are "for girls," and boys are discouraged from consuming such things. Meanwhile, little girls grow up reading media that does not always reflect themselves (and if it does, it is not always positive or empowering). It is for this reason that I think more women have a higher sense of comfort in using male leads (as Kura pointed out). We grew up reading books about everyone and may even think the male character is a safer choice that will offer us more options. But a man who was discouraged from reading books by women or with female leads while growing up may not have any sense of comfort with writing women. This probably spawns the idea that we write characters like ourselves. My characters are not me.
We can learn empathy through reading, and having media that does not have diverse characters is a huge drawback. Previously, a lot of characters got slammed into special categories, so a fantasy with a gay lead would be considered "LGBT" or "Special Interest" rather than "fantasy." And fantasy with female leads? Perhaps you were never been exposed to it until now.
That's changing. Genre readers need diversity, too. If it seems there is a lot more equality and diversity in protagonists (fantasy and not), then that can only be a good thing! It is also very likely that at least half of all webcomics are done by women (though I don't have numbers, it is just based on my experience), and it may be something you are picking up on. I have seen more female leads in webcomics than I have in a lot of other areas (television, games, etc).
I think characters are for exploring, for asking questions, and obviously … for telling a story. I do have a male main lead in a fantasy, simply because when I created characters they were almost always men. In fact, a main woman did not show up until chapter four! Out of all characters introduced so far, only two are women. Eight are men. There is diversity in other ways, but I find the ratio of men to women unfortunate when I examine it now. I didn't know I did that default character thing until I learned about it well into the first year of the comic, and … I don't regret having a male character. But I do know that I will be working hard to make my female characters just as interesting, real, and complex as the males.