This is both a suggestion and a bug... When there is a raid near a witch, the witch should join the raid attacking the villagers. When I kill a witch while im defending a village I expect it to be part of said raid. Its infuriating, and I thought it was a bug.
It is intentional that witches don't attack villagers.
Also, keep in mind that this site is for bug reports only. For feature suggestions or changes please see: Minecraft Suggestions on Reddit.