Board Thread:Naruto Discussions/@comment-29393962-20161111215453/@comment-6769189-20170118225255

Thekillman wrote: Rasengan has a melee application, which is weird as well...

But the practical reason? Bijudama are reasonably easy to obtain for a person whereas TSB's arent. And it's especially easy if he really did have Wood Release and was the progenitor of the Uzumaki. Rasengan doesn't explode on impact.... Rasengan is based off of the TBB so presumably thats as close as humans can get. TBB are also super heavy. The positive/negative or black/white chakra seems to be a form that only the bijuu can access/process.