If this were true, then wouldn't folks just need an application binary that statically links all of its required libraries and resources into a giant, say, ELF? Why even bother with a container?
Anyway containers go quite a bit further than just static linking, most people aren't out there linking all the binaries that their shell script uses together?
It's not possible to package half a Linux distribution into a single binary. That's why we have containers.
Personally, I use containers to quickly spin-up different database servers for development or as an easy way of deployment to a cloud service...
That said, it makes sense from a developer POV; if, during development, you don't need the isolation you can run multiple containers (with on paper fast boot times and minimal overhead) on your development box.
There's plenty of cases to imagine where you need the containerization but not necessarily the isolation.
so people use containers instead (even if the container literally only contains a single statically linked binary)