I once asked the supervisor friend that work in Customs: don't you guys get all that information when you scan our passports (including job and reason for visit, THEY KNOW), and he smiled and said yes. So I say WHY THE F would you still torment me in filling out those forms (I have 6 children, we go in and out of China frequently), and he smiled and said "I don't know, we throw away those forms as soon as we collect them, but someone upstairs still insists on them"