Q. Is witchcraft for women only?
A. No, men are just as welcome to practice witchcraft or follow the Wiccan religion as women (but they are not called warlocks). There are more women who are Wiccan mainly because the Wiccan religion allows for female-oriented worship, where most other mainstream religions do not.
Wiccans believe in both a God and a Goddess, so practitioners of the religion can focus on either one depending on their own needs. Women tend to worship the Goddess, and men tend to worship the God. Of course, this is not set in stone. We all relate to the Divine (either male or female) in our own way.
And of course, witchcraft itself has no religious overtones to it and gender makes no difference.