I mean, it's the whole "invisible teapot orbiting Mars" thing. Basically you can't disprove many of these hypothesis, so the logical prior is that the most "mundane" explanation for something has to be true.
I do think it can be taken too far however - particularly when it comes to searching for evidence of alien life. I mean, consider the whole Oumuamua debate. The first object is detected entering the solar system from the outside. It's unusually long and thin. It managed to use the sun as a gravitational slingshot, and even mysteriously picked up speed after passing the sun. A few non-crank scientists have suggested that maybe the simplest explanation it's an automated alien probe, but the general belief is we can only believe that to be the case once every natural explanation is exhausted. The implication here is intelligent aliens are, if not an invisible teapot orbiting Mars, unlikely enough that you have have a very high burden of proof.