My question is: why do we see life on earth ?, like life in the universe has infinite ways or forms and need not be equal to the earth Mars, that's anthropocentrism.
We have only lief on Earth to use as a reference. We also have stories of Alien races that have become as clear as reality even though we have no proof
Our arrogance tends to want to assume we are the highest form of evolution.
"And God said Let US make Man in OUR image, in OUR Likeness"This is what we do we assume that basically they are similar to us. It is hard to imagine an octopus build space craft so we have decided that two legs two hands is the best form to build interstellar craft even if they look a tad different like G'Kar

But since the Universe is so huge... why could their not be similar life forms out there? Chemicals and elements are limited (about 126ish in all) Since chemical combinations work in specific ways it is logical to assume that repeats will occur
Water is a good example No matter where you are in the Universe when you put hydrogen and oxygen in the same room you will have water
And the other factor (not counting a creator God) is that we could have been seeded here and thus LITERALLY "Let US make Man in OUR image, in OUR Likeness"