Why is the rum always gone, or in my case, left out?

Last night my mom and I made a cake from the cookbook, Mastering the Art of French Cooking. We made a chocolate almond cake, with delicious chocolate glaze/icing. I had to do a practice round before I make it for her birthday. My mom made me leave out the rum extract, darn it. I informed her I was part pirate, but I guess that didn't work. Maybe next time :) But until then, I'm excited for my parents to come home and try it out with me.