After he snapped his finger, his gauntlet got severely burned. I was wondering if Thanos still had use for Eitri.
Eitri was spared because he agreed to do what Thanos asked him to do and did it spectacularly well. His reward for his cooperation was that he was left alive. The fact that his hands were removed (to prevent him making weapons capable of killing Thanos) would strongly suggest that Thanos didn't see any further use for him.
Eitri: I thought if I did what he asked, they'd be safe. I made what he wanted. A device capable of harnessing the power of the stones. And he... and he killed everyone anyway. All except me. "Your life is yours," he said. "But your hands. Your hands are mine alone."
What's quite interesting is that Thanos murdered all of the dwarves rather than just half of them. Then again, we've seen him destroy entire populations (Knowwhere, for example) before, so it might just be that he's not consistent when it comes to space stations.