Anything that is too heavy for a driver to pick up is a freight package, and it requires a whole different network to move it around.

Physical packages cannot go through the same trucks. The conveyor belts are too narrow for freight for pallets...etc.

Meanwhile, package delivery companies own their logistics end-to-end, which enables simple conveniences like tracking. Freight is too large in volume to be operated by just one company, and as a result, user experience of shipping is very distributed.