But the chances that we will ever see life on other planets or they will come here: appx. 0%
Also, who's to say that life on other planets hasn't already come and gone? Universe is about 13 billion years old, give or take a week. Earth has been around 4-1/2 billion years. Man has been around only for a couple of million years of that, and recorded history only goes back a few thousand. That's an awfully small window for another civilization to hit.
Because we have all the science figured out, and travelling those distances is impossible.
Did you ever image that there could be societies that first harnessed electricity 2 million years ago? - making us .0000001% as technologically advanced as them.
Well?
I guess you probably think we know all there is to know about physics and faster than light travel?
I believe 100% we are not alone, and we have plenty of evidence that we have been visited in the past.
I would bet Columbus would say the same thing if you told him that one day aircraft would fly across the Atlantic in a matter of hours.
I have come to the same conclusion. The precise conditions required to sustain life make it seem that intelligent life may be fairly rare.
But even if it were not so rare you would still need the civilizations to exist at the same point in their technological progress so both could communicate with each other ... and located relatively close to one another. There is not much point in communication between galaxies if it takes 2.5 million years to send a message ... or even between stars on opposite sides of the Milky Way. There could have been hundreds of intelligent civilizations in our section of the Milky Way but they may not exist any more.
Thus you could have a situation where there have been millions of intelligent civilizations that have existed but few or none of them exist right now relatively close to us.