Sure but most web apps are more than a single binary. There's generating static files, a database, background worker / cache, and more. Then there's wanting to be able to develop that project as a whole on Windows, macOS and various Linux distros as well as deploying it to a specific distro of Linux (most likely). Then there's the distribution of the binary across a network in a reasonable way.
Docker and its ecosystem of tools solves all of those problems once your app is containerized. And if you want to go 1 step further and run a distributed system with load balancers and friends, container orchestration tools let you solve this problem at a level above your application.
And the best part is you can do all of that in the same way with any tech stack.