Well, it does make sense to look at a "habitable zone." Maybe not habitable for other life forms, but for Earthlings, it is.

And that's the thing. The only life we know is from Earth. So, most people will research planets that look like ours because we certainly know h20-like planets could harbor life.

And there'll probably be someone out there who is looking at the other planets for life forms, but not much.

Why don't we mainly look at the moon for life forms? Because we don't have any life forms made from rocks here on Earth. So it doesn't make much sense to extensively look for it there.