This process is ensuring that the right kind of products are shipped out in the right quantity, when the importer places no trust in his supplier or when several suppliers bring their products for consolidation.
It can be a worthwhile if the buyer has a precise loading plan and needs it to be respected very precisely (e.g. some cartons are too fragile to be placed at the bottom), or if the packaging is not conventional (e.g. some garments hung on bars, with no carton protection).