Containers are to a large extent a solution to an artificial problem. It your app is a single binary file + a single text configuration file with no dependencies apart from system libraries (i.e. libc POSIX) then you don't need a container, you're just a process. Containers are necessary because applications now consist of hundreds of small files with complex inter- and external dependencies.
Containers don't provide additional security, nor do they provide additional ways to restrict resources. If you want to restrict resources or sandbox programmes, you can do so without containers.
Unfortunately the hierarchical structure is lost in the name. It's one flat string and '/' and NUL have special meaning.
In a way, containers show that there is a legitimate need for multiple roots.