You labor under what we already know, not what could be. Many people have seen something, and those are credible witnesses. Instrumentation has tracked objects doing things our craft cannot do. It is not very scientific to assume those things were not observed just because we cannot explain their behavior. It is much more scientific to assume there are things we do not know or understand and work from there.
100% there are no creatures from other planets circling the earth. The distances are so freaking long, physics makes it impossible. If those creatures are really capable of reaching earth, why not land and get acquainted? WHat is the gain travelling zillion miles to visit earth and not landing?