Since I don't have a dishwashing machine (and I wouldn't use it all the time even if I had one), these Stackable Cups would come in handy -- especially if I have a full load to wash. You may be asking, "How so?"
Well, I don't know if you have noticed this before (but I"m sure you will now), cups take up a lot of space. Plates are relatively thin, cutlery has it's own spot, but cups can easily overflow beyond the confines of the dish rack. These Stackable Cups solve this congestion problem.
With protruding bumps on the out outside of the Stackable Cups, you can pile them without the cups getting stuck. This also increases airflow and hygiene.