»why the ships?«

I dont know if this question had been asked before but
I will ask it anyway


why do the rebels in THE MATRIX movie can log into the matrix only from their ships? some says that it's becuase of not letting the machines know the code of zion but that doesnt make sense to me, so any one know why?

So there in Broadcast level. Zion is not in Broadcast level.

"Dozer, when you're done, bring the ship up to broadcast depth, we're going in"