Transparency or masks offer flexibility to your photos:
change the color of the background;
overlap products in a collage;
add shadows;
create more compelling marketing materials;
Advanced Editing
Transparent backgrounds give the basic start to change the background of an image, group items together, add reflections, graphics, text, etc. You can see here some graphics examples.
Overlapping
A clean background will allow overlapping objects. Opens the door to more fancy effects.
Collages
Get items closer together without the risk of overlapping backgrounds. Editing is necessary to create a transparency mask.