Because, you will begin planning what to do with said chickens. You will allow yourself to hope and dream about life after the chickens. You will imagine how it would be to use the promised chickens to pay off all the bills and FINALLY be debt free. You will tell yourself, "I can get through these next lean months, because when the chickens come, it will have all been worth it."
It is not nice to promise a girl a said amount of chickens. It would be better to not say anything, and then, if the chickens come, it would be a happy surprise. This way, it's a depressing disappointment.
Dang those stupid chickens.