I'm not sure I understand the question either. But I'm guessing you mean something along the lines of - why isn't a midwife a witch?theoldlibrarian wrote:Why does a witch have to be a witch
The difference seems to be to do with magic, even if most witches try not to use it. In the Tiffany books, Granny Aching seems to be a witch even though she doesn't dress like one or acknowledge herself to be one. Indeed, in Tiffany's part of the Disc it was positively dangerous to be a witch.
A Discworld witch is a practitioner of magic with the advantages (or disadvantages ) that brings. So a witch can see Death and knows when she is going to die, and she can manipulate the magic field of the Disc.
In the Ramtops, it seems that letting everyone know that you are witch, by dressing like one and acting like one, is an important part of the magic. It gets respect and the community, although they might not like the witch, will have a certain amount of pride in her and make sure they look after her.
That's why it is such a bad thing in Wyrd Sisters when the Duke spreads rumours about the witches. If they lose that respect, they lose a lot of their power.