[timokau]

(I package sage for nix)

The problem is that sage actually depends on Octave, Maxima, R and many other packages. It parses binary output of many dependencies and often needs the exact version it expects because of that. It also has relatively brittle doctests testing everything an as a result often breaking on minor changes in dependencies.

If you have too much time, there is a very lengthy discussion on this on sage-packaging: https://groups.google.com/forum/#!topic/sage-packaging/ZJmJZ...