Because they had to do their part in moving Jey and Jimmy on, plus they need to be in a bit of a holding pattern until they're past the Saudi show, since Sami's not allowed in and KO also won't go. And especially with all the tag teams that came over to Raw, there's a bunch they can do now. They can fight off Priest and Balor (or Priest and Dom) from Judgment Day. They can take on the Good Brothers. Shit, Ciampa's coming back- Sami and KO vs. DIY would hit REAL nice. And that's before we get into Sami and KO's interpersonal chemistry and history.

Like, even if Cody won at Mania, there are some story beats that the Bloodline still have to hit before the Usos can be moved on independent. Besides, we KNOW they can carry a story- look at their wars with New Day. That was while Roman was Hulk Cena.