> IO is the same speed for all languages, so it cancels out.

That's not true, particularly in concurrent systems. Recent improvements to Go's scheduler (that make it more aware of various I/O concerns) have made it 2x faster under some workloads. You don't just optimize the compiler to produce the tightest code, you must also finesse its integration with the rest of the world.

> Not really a common use case.

If you say so.

> I don't think command-line-tools are Go's or Java's niche.

There are a lot of Go command-line tools out there. I think Go is a superb language for this area.