It probably didn't see that much use, as it struggled to find a niche. If you wanted intelligence tasks, Sol was cheap enough and much smarter. If you wanted performance and cost-effectiveness, Luna was significantly better value while being only a little less intelligent.
Terra ended up just being an awkward middle ground that was not particularly suited for any workload.
The users of Terra disagree. Specifically, Terra is useful when medium-grade intelligence is needed in instant ("none" thinking) mode.
I have found it worked quite well as the workhorse model in my hermes agent.