This is no different from asking someone the fastest route to get to the store and being told "go a mile down that road and take a left" even though the person didn't check to see if the road was temporarily blocked. If you ask someone directions, they're probably not going to add "unless the road isn't temporarily blocked" and "unless a meteor hit the store last night and I didn't know about it yet" and "unless there's a quantum fluctuation that will move all your molecules right next to the store".