Why not just contribute the changes they need upstream where possible, and maintain a repo for additional "scientific" packages (or just fork and start new projects) when that strategy doesn't work?
Because then they would no longer have complete control over what gets in their packages. In a place like CERN, total control is something people like to have.
Thanks, but and maintain a repo for additional "scientific" packages (or just fork and start new projects) when that strategy doesn't work