So in the end the removal of the Ruby dependency should clean up your local machine ;)
Go applications do require a runtime, but the executable is statically linked, so the binary executable ships with the runtime.
The rest of what you said is correct. The only reason you need the Go development tools installed is to develop the application or to compile it from source.
This is why the source is available. Implementation in Ruby, or any other interpreted language, does not guarantee compatibility. Not all systems have current interpreters or dependencies.
I agree that Ruby is likely already installed on those, but having watched co-workers fight version dependency problems with Ruby Gems on OSX, I tend to believe nothing is a universal solution.
Provided correct versions are in place.
In my aforementioned observations, Gem installation was complicated when the parent app relied on gem versions below the code currently in GitHub.
This is of course a problem not unique to Ruby (see: Default Python version on CentOS), based on the number of versioning utilities for Go. I have also had plenty of problems with autoconf's that don't work.
I've done some work cross-compiling golang on platforms that are not yet officially supported. I think you'll find the support is really remarkably good.
So your arguments is basically "I'm a Ruby user" ?
I'm neither a Go nor a Ruby user, but I have Go installed on more machines than Ruby... and Ruby is a requisite for running unlike Go!