You now see an extension of a principle tenet of US law applied to immigration: You are presumed innocent until proven guilty. In this case, the US assumes you will leave when your visa expires. Unless you are picked up for some other reason (like breaking the law somewhere) and found to be overstaying your visa, the US assumes you are honest. Most times, you will get away with it unless you cause trouble somewhere. Merely overstaying your visa is not something so serious that anyone will track you down to confirm that you have left.This sort of thing applies to ALL law enforcement in the USA. Robbers and thieves get away with their crime about 90% of the time. But such people tend to keep doing bad things and eventually get caught and convicted. 10% conviction rate is enough to deter most such crimes. People break the law by all the time by speeding, and might only be caught once every few years. The conviction rate is probably a fraction of a percent. At the other end of the spectrum, more serious crimes are pursued more rigorously.. we donu2019t want murderers running loose.