Edit to add:
Other than maybe standing up and p***ing into a moving shot-glass, there isn't anything that women aren't capable of.
martialarts.stackexchange.com/users/4/Alan
Women are under-represented in martial arts generally, not just in tricking.
It isn't that they aren't well-suited.
I think this is a culture problem more than a physiology one (though physiology does play a part).
The culture problem I'm speaking of is mult-faceted, but boils down to the overwhelming masculinity in martial arts culture.
Women can feel out of place in such an environment and, all too often, they quit because they don't believe their physiology is suited for the task, and more importantly, they don't feel they fit in.
On the other hand, I've known a few exceptional female martial artists.
You're less likely to meet these women, however, simply because there are fewer women who stick it out in martial arts.
martialarts.stackexchange.com/users/1462/The Wudang Kid
Yes, I agree with Alan's answer that women are quite able to perform at a high level in gymnastics, so tricking is not a problem for them physically.
And I agree with others that there are generally more men in martial arts than women, so that is a part of the explanation.
Then there's the fact that there really aren't many "tricking" classes offered, period.
There are lots of gymnastics and cheerleading classes, however.
In many cases, the only place you'll find tricking instruction is on youtube.
Lastly, gymnastics and cheerleading are culturally more social than tricking is.
According to psychology and sociology, women emphasize relationships and being socially connected more than men do.
Guys, on the other hand, care more about the action itself, how it makes them feel or look, rather than whether it also leads to forming closer bonds with their friends.
And so since tricking typically doesn't have many people in the class, or even any class at all (just youtube videos), guys more than girls get interested in it.
The way ahead if tricking is to become more balanced between the two sexes is to make tricking instruction more available, more social, safer / more professional, and less seen as a martial arts activity and more like a "performance" activity similar to contemporary wushu kung-fu, gymnastics, or modern dance.
martialarts.stackexchange.com/users/1555/Steve Weigand
While individual cases are, of course, individual cases, I would actually argue that there may be physical obstacles that reduce the incidence.
Women have a different center of gravity, enough that a different roll is suggested for parkour , and, not to be indelicate, but many women have an additional mass on their chest which makes rapid rotation around their vertical axis more awkward.
Neither is insurmountable, but it means that there are additional modifications needed to adapt the current techniques, which means that you have to be even more dedicated to get into it.
martialarts.stackexchange.com/users/1780/Macaco Branco
It's not because its easier for us, more just because, well, I don't know how to say it, other than that we love it.
Martial arts.
Knowing all of these really awesome and fancy ways to beat the crap out of someone.
As for tricking, Your right.
I haven't seen all that many girls in the sport.
But that in no way shape or form means its not a womens sport.
I Sparred with this two girls at my last tournament.
One of them was the stereotype.
Didn't practice.
Didn't train.
Didn't condition myself.
So after winning without breaking a sweat, I was about to face the other girl.
2 seconds into the match she did a jumping 360 roundhouse to my head.
I hate it when women think that just because they are women, mean they have to be lesser than men.
Its not at all true.
Do what you love, and don't let anybody stand in your way.
martialarts.stackexchange.com/users/1655/coltonon
I practise Taekwondo and am amazed by all those flying kicks and flips and everything.   But when I was on YouTube watching tricking videos, I saw only a small proportion of women. Is it because less women practise kicks? Or is doing kicks a hurdle that is really hard to overcome?
Are women not suitable for tricking?
martialarts.stackexchange.com
<tae-kwon-do><kicking>
martialarts.stackexchange.com/questions/2477
martialarts.stackexchange.com/users/281/Lai
Women are under-represented in martial arts generally, not just in tricking.  Women have a different center of gravity, enough that  a different roll is suggested for parkour , and, not to be indelicate, but many women have an additional mass on their chest which makes rapid rotation around their vertical axis more awkward. Women are generally under-represented in martial arts and have a different centre of gravity as well as an additional chest mass, making rotation around the vertical axis more awkward. 
Women are generally under-represented in martial arts and also have a different centre of gravity and an additional chest mass making rotation around the vertical axis more awkward. 