Witchcraft is a practice, a living discipline. Wicca is a religion where its practitioners sometimes include the practice of witchcraft, sometimes not but usually always include ritual or rites of reverence to their gods/goddesses.

Not all people who practice witchcraft are Wiccan.  They can be of other traditions but that use witchcraft to accomplish various purposes and goals.  

Some Wiccans do call themselves witches. Some do not for whatever reason.

There are Witches who do not identify as Wiccan because they see their particular practices as part of another faith or if they are pagan they view their practices as stemming from a time before Wicca was brought to light in the 1950s and so self identify with that or because they do not practice Witchcraft in the particular religious context that Wicca gives to its practices.

Myself for example: Broad category: --Pagan sort of an umbrella term for someone of an earth based spirituality-   Narrow it down: --Witch-- sort of like the old style village witch inclined to celebrate seasonal changes and look after the Earth. I do not identify as Wiccan. I relate to a time before Gerald Gardner brought Wiccan practices to light in the 1950s. I further identify as an atheist. I practice the craft without a religious context....

Peace