Why isn't Hydroamination of unactivated olefins seen in early to middle transition metals?

Answer 1

hydroaminations works using titanium as bisamidates or titanocenes, tantalum is also used, and some examples with the lanthanides Sm and Nd.
I found also an example with catalytic NBS.

I think that you probably need large and electronically soft metals, that can act as lewis bases.
early transition metals are to hard (like V or Sc)

Answer 2

I guess you mean why they can't catalyse the reaction. The reason is absence of valencies in the d-orbitals.