First thing that comes to mind is the need to link against libraries across platforms. Imagine that my app depends on opencv, if I wanted to statically link everything on my Windows machine, I need to compile opencv for Linux on my windows machine (or use pre-compiled binaries). Also, if you link against libraries dynamicaly, it's likely you can compile them on the host machine (or in a container) with more optimizations enabled. And the last thing is probably the ability to "freeze" the whole "system" environment (like folders, permissions, versions of system libraries).

Personally, I use containers to quickly spin-up different database servers for development or as an easy way of deployment to a cloud service...