Why are we looking for just earth-like planets?

Because our own planet will need to be replaced one day and it would be very wise to know where other habitable planets are that could support our species. Although our sun likely has many more billions years of life, one day our sun will go super nova and engulf our entire solar system. Since we would need to be able to travel at least close to the speed of light to get to another habitable planet in time to save our species, it seems very wise to at least know where the closest one is. In addition to the end of life for our star, there are other things to consider like comets and asteroids or other solar systems that could likely collide with our own. The collision of solar systems is actually quite common and we happen to be a part of a very busy galaxy that is unpredictable. And if we do want to find life, it seems logical to first look for life that might be somewhat compatible with our own. Since we cannot breathe on planets with poisonous atmospheres, it seems rather silly to want to go to those first.

It's a shot in the dark kind of thing. Overall, an attempt to prove that this galaxy harbors life on planets other than Earth. Chemistry is pretty much the same all over. Oxygen is the powerhouse and Carbon the framework. Now, what evolves is a different story but for a critter to accomplish what humans have done, it has to be able to manipulate and build stuff along with a highly functional brain.

Convergence is demonstrated with frequency on this planet so why not on others?

Firstly, I do hope that you realise that there is vastly more to astronomy than the overhyped search for boogiemen in space. No offence, but it looks suspiciously like a great many people think astronomy revolves around scanning the heavens for microbes! There is far more to it than that.

Also, questions about life are principally questions about biochemistry, not astronomy. Life depends upon biology and biochemistry. Astronomy has little to do with it. Only trying to help you understand this.

As to your question: it is best answered as follows: Look at the Earth. The Earth rpesents a great many diverse environments for living things. It has done so for over four billion years. Yet despite all the time available, and literally mountains of silicon, we only ever find life based on carbon, and it only thrives in the most hospitable places.

True, some species are able to exist by metabolising gases and substances such as hydrogen or methane, but all organisms require oxygen as part of their DNA and cellular structures. No oxygen, then no life. Even those so-called extremophiles need oxygen for their structural components.

Cheers!

We're not, astronomers are looking for all the extra solar planets that they can find.

Folks in the pop media are seemingly most interested in Earth like planets, for the reason that most people are most interested in the question if if there are other Earth like planets.

For the obvious reason, we don't know if life can form and develop in other atmospheres and environments. If we had evidence of life doing that, then we'd also be more interested in planets where that could happen, as well. But, as the only kind of life we know of needs a planet where liquid water can exist on a continuing basis, then that means that we will be extra interested in finding planets where that can happen.

The scientists doing the search haven't preferred Earth like planets. Now that we have found planets, larger and hotter than Earth, the effort is to find Earth like planets, so we have balanced picture = Earth like planets are harder to find, but of more interest to the media and the public.

I don't know about the other people here, but I want to meet Venusian women. They are said to wear shiny metallic form-fitting outfits and have a hypnotic gaze. When they look at you, theremin music starts playing in the background.

Uh....common sense? Why would we look for planets we CAN'T live on?

we dont know that yet.