Even if you're not in a situation where you might need one of these it might be situations where using one just makes more since then using a full size washer. Say you just need to wash a full diapers or some dedicates or just a few small things.
Well, it would make since to wash them in a full size washer and maybe you don't want to wait until you have a full load. That's when one of these minis would come in handy.