Given that we are the only habitable planet (that we know of), how incredulous is it that movies like Star Wars and Star Trek always visit such exotic planets with weird inhabitants?
No, it's not totally incredulous.
On earth itself, life has evolved in the most extreme conditions, some in conditions that have surprised scientists:
Scientists have not even given up on finding signs of life on other planets or moons within our solar system. There are indications that Mars and Europa, for example, may or may once have had conditions necessary for microorganisms.
Of course what we're interested is intelligent life, not microbes, etc. But the fact that life can take hold and adapt to such a wide variety of conditions means, as they say in Jurassic Park, that "life will find a way".
It then becomes a game of statistics. Theorists differ on the chances of extraterrestrial life, or more specifically, intelligent life, but extremely few would suggest there is none.
More exoplanets have been discovered than once estimated:
And there may be 40 billion earth-sized planets orbiting within the habitable zones of sun-like stars within our galaxy alone:
Looking at earth, there's more than one candidate for intelligence life. Gorilla and dolphins, for example, have been able to communicate with humans through sign language, etc. And neanderthals and cro magnons once co-existed.
It is doubtful that more than a small percentage of habitable planets would develop intelligent life, but there's nowhere near 40 billion alien species in the Star Wars films.
Plus some moons may be habitable. So maybe there are some Ewoks out there.
And if your issue is with the exotic quality of some life, you need look no further than earth. Case in point: siphonophorae.