It's the dependency hell problem as packages are added to the sandbox environment. If they were just shipping python (standard library), it would be fine, but all of the useful libraries have large numbers of dependencies.
It's not hell because they carefully curate the set of libraries rather than having end-users attempt to have every combination of packages (and then blame microsoft for the dependency hell / lack of support for their exact configuration.).
You say this as a good thing... but as a data scientist that uses python every day I can assure you their "carefully curated set of third party libraries" definitely will not include most of the libraries I rely upon for my work.
