[vidarh]

Mostly it comes down to lack of experience with containers so far, and lack of tools.

Most apps need very little from the underlying OS if you actually take the time to e.g. set up a toolchain with a build container that you then move the build artefacts out of to install into the final container. Instead you see a lot of containers that in effect include all the build dependencies and a nearly full OS pulled in by that.

It is improving, though slowly.