Why is it that, I'm just not in the mood a perfectly good excuse for one gender but not the other?

That's an easy one. It's because women are bad at being turned down. Men spend our lives approaching women. Sometimes they accommodate us with a phone number or a date, an invitation to action or the answer yes to a wedding proposal. But...more often than not, they turn us down and that's OK - it's part of life. Men start practicing this in our teens. Women don't so if they are turned down, they take it much worse than we do.