Because you didn't want to set an env var?
People† at large just want to clone https://github.com/foo/bar.git wherever they see fit, like directly at ~/Workspace/bar, ~/work/bar, ~/projects/contrib/bar or even /tmp/bar.
† "People" includes CI systems that expect the typical "clone and cd straight into" thing to work, resulting in a lot of boilerplate and/or symlink hacks to work around such expectations.
You haven't needed to set a GOPATH since 1.8, which was released over a year ago (we're now at 1.10). Since 1.8, the Go toolchain will use a default GOPATH; the environment variable is only needed as an override.
but on ci servers it could be akward.