The reason to believe this is that I think the evidence so far tend to support that statement, not the opposite.
You may object my statement to show some hubris, for how can we know.(I am not even qualified by anything but some reading/interest and my head. The last may not impress You!But then make your counterarguments!)
Why tehn? It is rather trivial, and I may even somewhat repeat myself: Those who believe that the "broad way" lead to "intelligent toolmaking" please give just two examplews (we all know the one I guess), out of "zillions"(perhaps some million living, some billions(?) extinct lifeforms. Very "impressive" record for intelligence, but OK:untill now one in a living planets lifetime after some thousand million years.
Life as we can recognise: One example for one stellar system.Whe should already have some evidence I think, if anything like life on earth were present at least more than sporadically other places in this solar system. So the evidence, though not strong perhaps, point all that way.
And I think the arguments that life or intelligent toolmaking "civilisations" "must" be frequent is simply ill founded.

I actually agree with your statement - intelligent life in the universe probably is rare. But you are not taking into account that there is billions possibly trillions of gallaxies, and each galaxy contains billions or trillions of stars. Your logic is right in my opinion, but the vastness of the Universe says that there should be other intelligent life out there if life is so abundant on our planet, then it is somewhat of a given that there will be life on other planets, however far away those planets may be from us.

Yes, there may be an infinite numbers. But they may be so far away that they will not be something science can study directly. Forever(?) a theme most for thought, not for observation or contact.

It is of course debatable as to whether there is intelligent life on Earth! Certainly the existence of politicians suggests that we are fighting a losing battle!!

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Of all the things I've ever lost, I miss my mind the most!

Oh darn it! You mean we may never make contact? so far away.
Well I hope you are wrong. very wrong.
Nothing would please me more than to have humanity jolted into the 21st centry by making contact with ET's. I fear you may well be right. :huh:
To grasp the enormaty of the universe is ferther complicated by the time it takes for a spiecies like us to evolve into some thing worth talking to. This planet has been here for about four and a half billion years. We have walked upright and showen singes of intelagance for as little as a million years. If the Jerasick period had not ended, would man ever have emerged?. No.
So lets not expect to find humanoid beings :unsure: what we will find is life. It may not be friendly. It may not be able to comunicate with us. On this point, Is there one other life form on this planet that we can comunicate with? No, not one.
When did your cat last tell you its raining. does your dog really like this food or that one. When we can talk with the Octopuse about its food prefrancess. we might be ready. not yet. :blink: :P

Life:

Mircrobial Life - now that we know planets around other stars are quite common then planets bearing microbial life may be quite common also.

Multicellular Life:- It could be that anything from only 1% to 10% of planets that support life have the conditions necessary to support large mulitcellular organisms.

Intelligent Life:- We only have the evolution of earth as a reference point. That said there were long periods where large organisms lived for 10s if not 100s of millions of years without showing much signs of moving towards technological intelligence.

In the past when people looked at humans they tended to see us as the inevitable end product of the evolutionary process. That of course was typical human arrogance, we are not the end product of anything. We just happened to be an animal with the right sort of potential that was faced with the challenge/opportunity to use the interaction between our higher capacity brain and our manipulatory limbs that allowed us to become (for a time at least) an evolutionary superpower. On many planets that may support large animals there may never have been a creature with the right potential, faced with the right sort of challenges which forced the pace of tool making and language. So its quite likely there many not be any other intelligent species within 100 light years of us and even some of those may not have yet discovered radio.

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Note 1. All requests for planetary demolition must now be submitted in quadruplicate on form UX-565/B4 and be counter-signed by the assistant administrative officer for interstellar traffic calming - department QG-7. Subject to approval by the chief planning officer and the infrastructure development coordination sub-committee.