Things that annoy me, Part 1

So can someone please explain to me why I am the only person who can rinse out a sippy cup. I just don't get it. The girls finish with them for the day, I open the top, rinse them out and sit them in drainer to be loaded into the dishwasher. Can anyone else do this? Apparently, no. Today under my mountainous pile of dishes I found 3 with old crusty, sour milk in them. Are you kidding? Stay with me here. They were in the sink.