Outer space is big. Really, really, really big with the nearest star system being Alpha Centauri 4.3 light-years away or 25 trillion miles.
The New Horizons spacecraft, travelling at 36,373 mph, took just shy of a decade to reach Pluto so if New Horizons was aimed toward the Alpha Centauri system it would take this spacecraft about 78,000 years to get there.
The sheer distance and time to travel from one star system to another could explain why nobody has turned up from other planets, could be they are on their way but as they only left on the trip to Earth 39,000 years ago so they are only halfway here.
Some people believe that they have already made the trip and have been a bit sloppy in quietly observing us and occasionally we catch them gawping at us.
A Close Encounters of the First kind is a visual sighting of an unidentified flying object and there have been plenty of them and there have been quite a few Close Encounters of the Second kind where a physical effect is witnesses such as interference in the functioning of a device or some physical trace like impressions in the ground such as crop circles.
A Close Encounter of the Third kind is where an animated creature is present including humanoids or robots but the Fourth kind takes things up a notch as it is when a human is abducted by a UFO or its occupants and may or may not include the use of anal probes.
A Close Encounters of the Fifth kind is communication with extraterrestrial intelligence and the Sixth kind is the death of a human at the hands of an alien and the final classification is the Seventh kind the creation of a human/alien hybrid, either by sexual reproduction or by artificial scientific methods.
The only issue we have to sort out now is if they turn up and ask to be taken to our leader, who we take them to because looking around at the leaders we have now, the aliens would be justified in zapping us into a black hole for wasting the 78,000 years it took them to get here in search for intelligent life.