Docker has a few more upsides than just bundling an app with its dependencies, orchestration being one of them. Also, a go app wouldn't have to be cross-compiled for whatever architecture as long as Docker runs there. Go makes that easy and effortless, sure, and there's nothing stopping you from doing so.

Docker containers inherit the architecture of the host system. There is no CPU virtualization involved. So you still need to cross compile if you want to run the binary on another architecture, regardless of whether or not the binary is running inside a docker container.