Our brains are very bad at handling big numbers, and it is quite often a limiting factor in our ability to grasp certain concepts. If your brain doesn't work correctly (which it doesn't with billions), then you might trick it into accepting the truth, or at least something closer than the truth. Whether or not marijuana or other drugs do that, and if they do, for which people, is a different story, but you are assuming that your sober state of mind is anywhere near rational, which suggests you've never actually been around a human being for an extended period of time.