So I was browsing tumblr like I totally shouldn't, and I saw a post about the latest Precure season, with a possible reason why they decided to go with a witch theme for this one.
The suspected reason is that it's in celebration of the mother of all magical girls, Sally the Witch, being fifty years old this year.
Whether or not this is true it's kind of a big deal imo. The series that started everything is now fifty years old and it's amazing to see how far the genre has come, starting out as a Bewitched inspired black and white show about a young girl with a wand, to taking on all kinds of forms from costumed crime fighters to mermaid idol singers to liches and even kigurumi detectives.
Now if only some of these older shows (especially Sally) were subbed. I don't know if they'd want to re-licenses a 50 year old anime, much less bring it to the west.