#3 She's Not A Good Promo

The one thing we've learned during her time in WWE is that, while she's had some pretty good matches, Ronda Rousey is far from being the best talker in the business. In her defense though, she doesn't need to be a great talker, she just needs to keep doing what she's doing in the ring.
However, there will come a point when she does need to start talking a little more, so to circumvent that, they might want to put her with someone like Paul Heyman, who'll presumably be free after SummerSlam.
But, for now, on her own, Ronda Rousey isn't going to "talk them into the building," and again, that's okay for now, but WWE can't continue to hide her lack of promo skills forever, unless they pair her with someone who can do most of the talking for her.