I agree with Clear_Prop. Imagine that you were a pax on this flight and it was your first time flying. If the pilot came on and said that he had to make a go around because he screwed up the landing and wasn't coming in right, you're not going to feel very confident that you'll get back on the ground again. If he simply said that there was something on the runway then you're not going to be so worried. Yeah, he lied to them, but so what? The lies were made with the passangers best interests at mind.
Anyway, imagine the news reports if he told them the truth. "As soon as I heard that the pilot wasn't able to fly the plane properly, I started praying to god. I just knew that it was the end, we were going to crash."