Because you can't throw an axe as far as you can shoot an arrow. Different tools for different purposes.

That's like asking, " if you can throw a spear, why invent the gun?"

I've managed to make it through 3 of the Origins episodes and I just can't get into it. How does Origins' Gibbs have even less of a personality than the NCIS Gibbs?

They made a mistake in canceling NCIS: Hawaii for Origins.