@DayoftheDante

Some plausible explanations.

1) Because it gave Kabuto another chance to look cool.
2) Because it wasted more time, pushing back more fillers by a few minutes.
3) Because this whole story is actually a gaiden of Inuyasha. The leader of Akatsuki (who is actually Naraku) sent those Saimyōshō to look find Orochimaru so he can kill him and retrieve the Sacred Jewel shard in his Sword of Kusanagi.