A lot of value in little weight
A pallet of phones, computers or components can be worth as much as a whole container of other goods. That has two consequences that define the entire operation. The first is financial: freight weighs little against the value of the cargo. In furniture or materials, freight can be a significant part of the final cost; in electronics, it is almost always a minor fraction. That changes the calculation of which route makes sense. The second is security: anything that is worth a lot, weighs little and resells easily is a target for theft.