That’s not the same as “collapse all”, though, because if you shift-click the root node, and then expand it again, ALL child nodes are still expanded, and you have to go through each one individually.
If you’re working with Datasmith imports, you can have literally hundreds of these, and it’s simply unmanageable.
Besides, shortcuts are undiscoverable, so to a new user, it’s as if the feature might as well not exist.