If I purchased my nexus 6 directly from Motorola, isn't it already sim unlocked?
Yes.
But for some of us we were unable to get one through Motorola or Google so we settled for the carriers. Even with doing that I will say At&t actually been pretty good about unlocking devices. Unfortunately it can take up to "5 business days" vs going the route of 3rd party that does it in 3-8 hours. So it is a matter of which route you choose to go.
@smalltowngirl13 , curious to see what kind of speed and how the Nexus 6 is performing as far as signal strength vs your other devices. So far for me it is leading the pack.