Board Thread:Off Topic/@comment-25936766-20170228175626/@comment-14138255-20170311013817

The Tau aren't psionically sensitive like the humans and Eldar (thus why they have no Psykers and travel space painfully slow compared to the other races, since they can't/don't want to use The Warp), and the Eldar are just looking after them and theirs (willing to sacrifice whole human worlds if it means saving just one of their minor ships), and their technology is also stagnating.