Why is Lishu one of the high ranking consorts?

I understand that the emperor keeps her in the palace to maintain her safety but couldn’t he have put her as a lower concubine? I don’t really know much about lishu’s family and background but from my understanding the high ranking consorts are there for political benefits. Is her family important? Also she is pretty young and isn’t the brightest and I think one of the lower concubines can definitely replace her positions because of their maturity and intelligence.