[zbentley]

A guess: it takes a long time to get a reliable network of mirrors (mostly spent building relationships with institutions, like universities, with both the bandwidth/infrastructure you need and the willingness to lend it for free), and Docker is quite new.

[dhzhzjsbevs]

Why would anyone give a for product company free stuff? You don't get to have it both ways. It's either open source or it's not and from what I've seen of docker, it's very closed.