It's kind of hard to tell because it's a low-poly model at a low resolution, but it looks like they're wearing the mask kuroko wear, who are stagehands in Japanese theater that you're expected to pretend aren't there while they move things around on the stage.
This is from Tomodachi Life, right? I haven't actually played it, but from what I know of the game, all the characters are Miis. So if the store staff were also Miis, there would be nothing to distinguish them from regular characters, so maybe they're trying to avoid giving the impression that you can interact with them in the same way as you can with regular characters.