> Could give examples of use cases where dense 3d packing is needed? (Say, besides literal packing of physical objects in a box? )

Not an answer, but something interesting on this topic:

In a warehouse/distribution center, a dense packing result can be too time consuming for most consumer products. As density increases, it takes the human longer to find their own solution rapidly that works. You can provide instructions but that is even slower than the human just doing their best via trial and error.

We had to dial back our settings from about a 95% volume consumption percent (initial naive setting) down to about 80% before they could rapidly fill the cartons. Basically it's balancing cost of labor vs capacity of system during peak (conveyor would start backing up) vs shipping costs.