- that packages follow semver
- that the OS packagers are in a better position to test package combinations.
If the author releases a new version of libfoo, and A, B and C in an OS repo depend on libfoo, then the OS packagers do not release a new version of libfoo until the tests for A, B & C pass.
These are two good assumptions, and the language package world would be in much better shape if they followed those assumptions too.