Why the same size machines, one is high conveyor and one is low conveyor ?

Usually the middle size machine like 100cm W x 80cm H and the big size machine like the 1.5m x 1.8m tunnel size machine， they usually check the big size and heavy luggage or cargo, so we make the convyor low and close to the ground, easy to upload the luggages/ cargo.

Small size machine usually check the hand held bags, so the conveyor is about 0.7m high from the ground.