> In a way, it seems like async Rust appears more often when you need to do io operations, and not so much when you just need to do work in parallel.

Yep this makes sense to me.

If your workload is CPU-bound then context switching to make progress on 10 tasks concurrently, is going to be slower than doing them sequentially.

But if it’s IO-bound you will spend most of your time waiting, which you could use to make progress on the other tasks.