#4 This allows WWE to flesh out the rest of the division

WWE is very much in a rebuilding mode when it comes to their women's division and they need to set up suitable challengers for Asuka in the coming months. With that being said, having Nia Jax as the first opponent to challenge The Empress of tomorrow allows for the company to get a plethora of other Superstars ready for the challenge.
In fact this is a great opportunity for WWE to flesh out Superstars like Bianca Belair, Natalya Liv Morgan and maybe even Kairi Sane before giving them a chance at Asuka for the title. At least this way, the fans have more time to get invested in these characters and will have a reason to care when it finally comes down to them having a match. A lengthy feud with Nia Jax is just what the RAW women's division needs.
Look who just shut down all of Tony Khan's critics! More HERE.
In the end, there aren't a lot of women in the division that are even ready for Asuka, which is why the company needs to continue to flesh these women's characters out. If they do so, there is a much better chance of creating something interesting match ups with the right payoffs at stake. While they do that, Nia Jax will be able to drag out a good feud with the Empress of Tomorrow.
After all, there's a lot of history between Asuka and Nia Jax. This won't be a short feud, and will give WWE plenty of time to build that division back up.